PELELEEPESL Ee rceeeccter cater 
A 
ETH 


Pereeatacerr 
aH 
' ety | 
ft Hen 


nth 
Hd 


tre 
aa44) 
HE 
THEE 


a 
ponte 
met 
eres 
tone tn we ns 
oe an ah Bes 
a 
rm et rt a 
av ae eee: 
eee 
rears 
eek 
ave een 
—— 
ie a 
~ 


acne 
—— 
i 
oe AS 
Ssoasal 


HE 
HT A j 
WEEE eth 
Ha Oe ate 


Ul 





Lay trash F he ei hy nat 


vi 

Pa | 
} LS ap A 
Wea ie eS rae 
if i” wi a ys } he ‘ 






YX OF PRIVEE > 
Ny aN 


oo) 


Py 


, ye 
or agicat sews 





ees QUEER 
Section W Zz 





ri) sat 
4 ah ie a. 


iy 


1 


the A 
(> 
gun 
cine 










‘in 2022 with funding can 
Princeton Theological Saery ti Lik 


Wy Mila 
ee ay 
, Pom 
i ain a4 


httos /Tarchive, org/detalls/evolutionforjohno 


J ‘ ' * i ia. j | 4 ‘es 


EVOLUTION FOR JOHN DOE 





apat OF Faia 
ie: Fr ee 
<1 Be OE fw4t* 


¢ gf 4 
“" 


OGi 20 1995 






Evolution for John D 


By | 
HENSHAW WARD 


With Foreword by 
LORANDE LOSS WOODRUFF 


Illustrated 


INDIANAPOLIS 
THE BOBBS-MERRILL COMPANY 
PUBLISHERS 


CoprgicHt, 1925 
By Tue Bosss-MerRiLL COMPANY 


Printed in the United States of America 


PRINTED AND BOUND 
BY BRAUNWORTH & CO., ING. 
BROOKLYN, NEW YORK 


FOREWORD 


by 


LORANDE Loss WoopRuFF 


Professor of Protozoology at Yale Unwwersity 


Mr. Ward has demonstrated in the present volume that it 
is possible for the layman to put in forceful, popular lan- 
guage a vivid, general view of what is meant by organic evo- 
lution. He gives just such a survey as a person unacquainted 
with biology needs for an introduction to some of the large 
problems of life—problems so large that they have burst the 
confines of the biological laboratory to trouble unnecessarily 
some politicians and theologians. 

The reader who has been curious about these questions 
will, I feel sure, find that his interest in the book grows as 
he proceeds, and will finish it with the desire to fill out the 
general picture he has obtained by turning to some of the 
eritical treatises which the author suggests. Mr. Ward opens 
the door, 





ACKNOWLEDGMENTS TO 


ALBERT GALLOWAY KELLER, CHESTER Ray LONGWELL AND 
LoRANDE Loss WoopRuFF. 


My dear Keller: 


If you would let me tell you in private how I feel about 
your share in this undertaking, I should not make you un- 
comfortable by displaying your name in such a public way. 
But since you will not listen, you must read. When you gave 
me the benefit of your twenty years of experience in teaching 
evolution without being a biologist, you showed the way 
through the maze; by giving criticism at every step you pre- 
vented a lot of blunders. I want you to know that I am 
grateful for making the path and trying to keep me in it. 

After you had been so tireless in helping me for two years, 
you went further. You persuaded Professor Longwell to 
eriticize the chapter on geology and to put me in his debt for 
some very useful comments. Then you enticed into my service 
a critic who could remove some technical mistakes, whose 
imagination was equal to sympathizing with this strange 
amateur enterprise, and whose kindness made him unsparing. 
I am sure you want to join me in thanking Professor Wood- 
ruff for this aid, of a sort that few biologists could give. 

No sensible scientist will find fault with him if he has not 
removed all the mistakes from this book, nor will readers 
blame you if my printed words are less racy than your spoken 
ones. You and he have done all that was possible, laboring 
with such generosity as I have never before seen in my 
struggle for existence. 

Henshaw Ward. 





CONTENTS 


Part OnE: A DESCRIPTION OF EVOLUTION 


WHat JOHN Dor THINKS ABOUT EVOLUTION . . 


THE MyriaAD Forms oF LIFE 
THe TANGLED WEB OF LIFE , 
THE VARIED MopES oF LIFE . 
THE JUNGLE OF ADAPTATIONS . 
THE STRUGGLE FOR EXISTENCE . 


VARIATION Pr cal Nele!, er ntt Mates Ul te 
HEREDITY ee he Reo 
NATURAL Sen ereeyate RNa Ween 


e 


Part Two: THE EVIDENCES OF EVOLUTION 


WHat ‘‘EvmpENcEs’’ ARE . . 


e ° ° 


THE EVIDENCE FROM THE RIVALRY OF Gaerne 


THE EVIDENCE FROM THE RockKS 


THE EVIDENCE FROM GEOGRAPHICAL Disa 
THE EVIDENCE FROM CLASSIFICATION 
THE EVIDENCE FROM ARTIFICIAL SELECTION 

THE EVIDENCE FROM THE STRUCTURES OF ANIMALS 


THe EVIDENCE FROM EMBRYOS 
THe EVMENCE FROM BLOOD . 


Part THREE: THE HISTORY OF 


LAMARCK St, RE Bl ain AONE 
DAT RULNGITN S et e BN oie hen ae RU ath 
WWI RLAN NS cr Uae Cini dann. Bog 
MENDELISM . . Sale une is 
DE VRIES’S te aa x 
How Evo.utrion Stanps To-DAY 
THE FospicK IDEA . 
BIBLAOGRATH Mons itis ca, ae tet ale 


InDEX PON tal oC CoO Oe eames 


1 


EVvoLurion 


109 
125 


.167 


169 
178 
204 
216 
231 
236 
252 
260 


267 
271 
286 
292 
301 
304 
332 
339 
345 


oe: 





PART ONE 


A Descriprion or EVvoLutTIon 





Evolution for John Doe 


CHAPTER I 
WHAT JOHN DOE THINKS ABOUT EVOLUTION 


Joun Dor thinks evolution is ‘‘the doctrine that 
man is descended from monkeys,’’ and he is so 
amused or so offended at this theory that his whole 
mind is occupied with it. His conception is ridic- 
ulously false. Until John Doe discards that notion 
and takes a fresh start, he will never understand the 
subject. Therefore any one who tries to explain evo- 
lution to him will fail if he pays the least attention 
to the ‘‘monkey doctrine.’’ In this book there is no 
reference to any ape-like creature and no discussion 
of the descent of man. 

John Doe thinks that evolution explains the origin 
of life. But no scientist pretends to know anything 
about the origin, and in this book nothing is said of a 
subject which is far beyond the reach of present 
human knowledge. 

John Doe thinks evolution has something to 
do with ‘‘progress’’—that it announces some creed of 
an onward and upward movement toward perfection. 
Evolution is nothing of the sort; it does not venture 
into any speculation about the meaning of life or its 
final goal. In this book there is no doctrine of ‘‘prog- 
ress’? and no philosophical reasoning. 

15 


16 EVOLUTION FOR JOHN DOE 


To the mind of John Doe there is something mys- 
tical and awesome about ‘‘Evolution,’’ especially if it 
is printed with a large H. The evolution in this book 
is usually printed with a small e and means only the 
very plain scientific theory that every form of plant 
or animal that ever lived developed out of a previous 
form. 

John Doe guesses that evolution is true, but he 
rather wishes it were not. He has a vague fear that 
the theory is materialistic and tends to weaken reli- 
gious faith. If he reads the opinions of eminent 
divines in Part Three, he will find that there is no 
ground for his fear. Recently a young Presbyterian 
minister said to me, ‘‘All our theology is now based 
on evolution.’?’ He represents the thought of many 
divinity schools to-day. 

John Doe suspects from head-lines in his news- 
paper that evolution is a debatable theory, that it is 
being overthrown every six months, and that it may 
be discarded before long. When he has read section 
four of Chapter XXIV, he will understand that evolu- 
tion is here to stay; there is no more chance that the 
theory will be disproved than there is that men will 
some time give up their belief that the earth is round; 
every reputable modern scientist believes in it as a 
matter of course. It is now an integral part of all 
general education and culture. To suppose that it 
may some day be abandoned is to live in intellectual 
barbarism. 

To the common horse-sense of John Doe evolution 
appears probable. ‘‘But,’’ he says, ‘‘it is not to be 
seen at work here and now, and so it looks dubious to 
me.’’ When he has seen the ‘‘billion-year movie’’ in 
Chapter XII, he will feel relieved. 

Mr. Doe supposes that evolution is extremely diffi- 
cult, so that he has small chance of ever finding out 


WHAT JOHN DOE THINKS 17 


about it. For this supposition he is excusable. It is 
true that most scientific books are highly technical, and 
that evolution is based on several branches of science 
at once, and that each is hard to learn about, and that 
the combination of several in one theory is excessively 
complicated. Also it is true that, to the best of my 
knowledge, no simple explanation has ever been put 
into a volume. For twenty years I have tried to find 
some book in a popular style that I could place in the 
hands of young men who were curious to read about 
evolution, and I have longed to find such a treatment 
for myself, which would give me in a few hours an 
outline of the information that is hidden in the forbid- 
ding tomes of science. I have examined several vol- 
umes that were said to be of this sort, but not one 
would serve my purpose. Librarians are constantly 
asked for ‘‘something simple about evolution,’’ but 
they have to shake their heads sadly. Apparently the 
biologists know so much of the details that they can 
not write a brief account of the whole theory. Not 
one of them has begun at the beginning of my ignor- 
ance and shown me, step by step, an outline of the 
whole. I see a lot of chapters about ‘‘Somatogen- 
esis’? and ‘‘Mendelism’’ and ‘‘Neo-Lamarckism,’’ but 
I am lost in a wilderness of big words, and I haven’t 
any sketch-map. 

Probably most intelligent people have tried during 
the last quarter-century to learn something about a 
theory that has remodeled all the world’s knowledge 
and profoundly affected its way of thinking. Last 
year I grew so desperate as to read a number of the 
standard works on evolution, and I was curious to see 
whether I could form a digest of the bewildering ar- 
ray of different branches of science to which all the 
authors have to appeal. I have written it out as if I 
were telling a friend about the knowledge that is so 


18 EVOLUTION FOR JOHN DOE 


new and imperfect in my mind. It seems reckless to 
publish this. Yet the signs are that no professional 
scientist is ever going to attempt this job that so sore- 
ly needs to be done. Some amateur must try. 

Evolution for John Doe is not a proof of anything, 
because evolution has never been mathematically dem- 
onstrated. It is not an argument, because there is no 
sense in a layman’s arguing for or against the entire 
body of learned men whose business it is to study 
organic life. It is merely an outline of what this body 
of scholars conceives to be the explanation of how liv- 
ing forms have developed. It begins at the beginning, 
with sketches of the facts, and gives descriptions of 
how scientists look at nature. 

If you are not familiar with the history of scien- 
tific thought and not too eager to begin to read of evo- 
lution, spend a couple of minutes with the next para- 
graph, which is about the theory that the earth moves. 
It is an excellent preparation for the chapters that 
follow. 

The normal human brain, unfamiliar with the facts 
of astronomy, can not conceive that the earth goes 
around the sun. A thousand generations of the most 
observant minds that earth could breed never sus- 
pected such an idea. Men learned to build great cities 
and to write poetry and to predict eclipses long be- 
fore they ever questioned the apparent fact that the 
sun moves and the earth stands still. Twenty-five 
centuries ago Babylonian astronomers developed the 
notion that the earth might be a globe suspended in 
space, and a Greek philosopher, three centuries later, 
argued that the earth moved; but very few philos- 
ophers during the next twenty centuries could take 
this speculation seriously. They could not feel the 
earth move, and they could see the sun move. Yet the 
fantastic theory of the earth’s movement lingered on 


WHAT JOHN DOE THINKS 19 


in philosophical writings and was considerably dis- 
cussed in Italy at the time when Columbus was pre- 
paring to sail west. Wild as this Pythagorean fancy 
seemed to most learned people, it appealed strongly 
to a Polish astronomer who was then studying in 
Italy. This genius, Copernicus, was equal to the su- 
perhuman task of fitting together facts and figures 
into a proof that the earth spins on its axis every day 
and travels around the sun every year. Yet because 
he made one wrong assumption, so that his explana- 
tion would not check with all the facts, most scholars 
continued to laugh at his topsy-turvy theory. Dur- 
ing the next two hundred years his proofs carried 
conviction to very few astronomers. The men who 
founded Yale and Harvard, like most of their con- 
temporaries in Oxford and Cambridge, believed that 
the earth was immovable and covered by an immov- 
able ‘‘firmament.’’ As late as 1800 there were many 
cultivated minds that believed it was irreligious to 
think of the earth’s rotating and revolving. Even 
down. almost to our own time the ancient belief was 
held by many in the United States; in 1880 a colored 
Baptist preacher of Richmond was still declaring that 
‘<The sun do move.’’ His famous sermon was not the 
vagary of an ignorant negro; it was simply conserva- 
tism, only sixty years behind respectable opinion in 
the foremost American colleges. With such extreme 
difficulty, after such prolonged controversy, can the 
human race accept a fact that is not directly apparent 
to the Senses. 

In a similar way there was current in the world for 
two thousand years a speculation that perhaps all ani- 
mals had developed from earlier and simpler forms, 
and those again from still earlier and fewer forms, 
and so on back to a beginning of all life in one lowly 
species. But this was sheer conjecture. Not until 


20 EVOLUTION FOR JOHN DOE 


some genius could assemble a vast array of facts, 
clearly organized as an argument, would the scientists 
accept so curious a belief. This feat was performed 
in 1859, when Darwin’s Origin of Species was pub- 
lished. So revolutionary a theory was bound to meet 
with opposition; but the argument was so thorough, 
and leading students of nature were so well prepared 
for it, that it soon convinced the scholarly world. To- 
day evolution is universally believed by scientists* and 
is regarded by zoologists and botanists as the funda- 
mental truth on which all their investigations are 
based. . 


*See the quotations in Part Three. 


CHAPTER II 
THE MYRIAD FORMS OF LIFE 


How many kinds of animals does an ordinary per- 
son, intelligent but untrained, know about? We have 
an answer in the works of Aristotle, as observant and 
intellectual a man as ever lived. It is probable that he 
was not acquainted with more than five hundred* spe- 
cies; it is doubtful whether many persons ever see in 
the region where they live more than two hundred 
species. I once asked a capable boy, who had studied 
a little school zoology, how many kinds of beetles he 
thought there were in the world; his answer was 
‘‘about three in every country.’’ The right answer is 
‘about one hundred thousand well-defined species, 
plus a greater number of sub-species or varieties.’’ 

The contrast between those two estimates is a fair 
index to the experience that every naturalist has as he 
grows in knowledge. The few common forms that 
meet his eyes near his home increase continually as 
he sharpens his sight and lengthens the radius of his 
collecting. The revelation, I remember vividly, came 
to me in this fashion: I was set the school task of mak- 
ing a collection of twenty-five kinds of beetles; this 
seemed quite an undertaking, for I could not count 
above a dozen kinds that I knew, most of which I 
called ‘‘bugs’’—potato-bugs, tumble-bugs, lady-bugs, 
June-bugs and so forth. But as soon as I opened my 
eyes, the new species appeared at every turn of the 


*Weismann says two hundred, but the index to the treatises on ani- 
mals contains at least four hundred. 


21 


22 EVOLUTION FOR JOHN DOK 


road, on every flower, under every bit of bark; the 
text-book by which I had to classify them named hun- 
dreds that I might never see; I learned of a mathemat- 
ics teacher who had gathered for his amusement five 
thousand species; I saw eighteen large volumes that 
were entirely devoted to the beetles of Central Amer- 
ica; I found that the world was swarming with myri- 
ads of beetles in endless varieties. 

Beetles, to be sure, are exceptionally numerous, 
but they are a fair illustration of the incredible num- 
bers of varieties that you would learn about if you 
devoted a few years to the study of any family of ani- 
mals or plants. This is the great preliminary fact 
that any one must realize before he can enter upon 
an understanding of evolution. The first step of ex- 
planation for a John Doe must. be to show him, in 
some kind of panoramic view, how the forms of life 
branch out into thousands and tens of thousands and 
hundreds of thousands of distinct species. 

In this chapter we need not define formally what 
is meant by ‘‘species,’’ except to say that it describes 
one sort of plant or animal that has some distinct dif- 
ference in its anatomy from all other sorts, and that 
usually can not cross or breed with other sorts. For 
example, cabbages and Brussels sprouts are not called 
two different species, because they are so similar in 
structure; all our domestic dogs could be called one 
species; all kinds of field-corn and popcorn are one 
species. But the grizzly bear and the polar bear are 
distinct species; a pocket gopher from Kansas and 
one from California, though they look and act much 
alike, have to be classed as two distinct species. With 
such a free-and-easy notion of what a species is, we 
may now take a flight over the world of life. It will 
be most convenient to follow an order from the small- 
est and simplest plants to the higher animals. 


Photograph, from a highly magnified glass model, of an animal which consists 


Ofsonly one ““cell”-’ (seepage 99). You are composed of 26,000 000,000.000 

cells, each of which, though not so showy, is as intricate a structure. This 

picture, like most of the others in the book. is made possible bv the care and 

artistry and generosity of the American Museum of Natural History in New 
York City. 





‘ ‘sdjod [e109 AUT} FO suoJOTEYS SY} FO 
posoduds st if ‘deop yooF YOST PUB OPTAL SO[TU 0G soov[d Ur ‘SuO, SaTIM OCZT St 9] ‘Sorpnys oinyeu 
qsig sty ope Ao[XN}F{ o1oyM ‘el[BlJsSnVY FO 4sBod YsvoyjIOU OY} FO Jooy Jolivg YBolh oy} FO HA V 





THE MYRIAD FORMS OF LIFE ~—_.23 


Wherever life is abundant in the world, every foot 
of space teems with invisible plants called bacteria. 
Some of these are so small as to be beyond the reach 
of the most powerful microscope, and are guessed at 
only by their effects in producing disease. Some are 
so short that fifty thousand of them if placed end to 
end would reach only one inch, and these are two or 
three times as large as the germ that is supposed to 
produce infantile paralysis. Bacteria multiply in such 
excessive numbers that the mind reels before the fig- 
ures. For instance, it is estimated that each human 
being is daily assisted in the digestion of his food by 
— several trillions of these organisms. Nor must we for- 
get that every individual of the trillions is a highly 
complex being which digests food by intricate chemi- 
eal processes and which reproduces itself by a mechan- 
ism that is so subtle and complicated as to be beyond 
comprehension. Bacteria are everywhere, living in 
the most varied ways. They (and closely related 
fungi) cause all the decay in the world and produce 
most of the contagious diseases. Upward of four- 
teen hundred species have been described. 

There are ten thousand* species of microscopical 
alge that produce slime, and six thousand more that 
produce a muddy deposit, the exquisite ‘‘diatoms.’’ 
There are four thousand species of sea mosses and 
kelp. There are more than fifty thousand species of 
those fungi that we know as toadstools and mildews 
and smuts. 

It would be of little use to asneiiae to set down 
rows of astonishing figures, for the mind can not con- 
ceive them nor retain them. But it is of the greatest 
use to appreciate, if only dimly, something of the ex- 
tent to which lowly forms of plants are diversified. 


*The numbers of botanical species are take from Ganong’s ad> 
mirable Textbook of Botany for Colleges, 


24 EVOLUTION FOR JOHN DOE 


Hiven so brief a glimpse as this at the wide expanse of 
life sets the mind to wondering, ‘‘How did it all come 
about? Why should there be so many different ways 
of living?’’ 

How many kinds of mosses have you ever heard 
of? If we had never seen but ten kinds, we could rest 
with the supposition that they were originally created 
so; but when we learn that there are sixteen thousand 
species of these inconspicuous growths and that the 
more common of the species have varieties that grade 
off insensibly into varieties of another species, then 
we can not be content with any such guess at the 
eause. The more a botanist becomes familiar with the 
countless varieties of plants, the more certain he feels 
that he is dealing with some sort of continuous growth 
of the whole system of organisms. A few dozen dif- 
ferent ferns would never have excited a Wallace or a 
Darwin to cudgel his brains for an interpretation of 
nature; but the four thousand five hundred species 
that botanists now know might well cause an inquisi- 
tive mind to he awake at night. 

All told there are about one hundred thousand spe- 
cies of this lower division of plants. Of the higher 
division, the flowering plants, there are more than 
one hundred and thirty thousand species. Some of 
the items that make up the total are five thousand 
grasses, one thousand palms, two thousand lilies, sev- 
en thousand orchids, one thousand two hundred eac- 
tuses. . 

More significant than mere numbers is the way in 
which plants unlike in appearance are found to be 
alike in their anatomy and way of growing, so that 
kinds which are very dissimilar in all outward ap- 
pearance are found to have inwardly a decided family 
resemblance. Thus elm trees, fig trees, nettles and 
hops are found to have such a similarity in their flow- 


THE MYRIAD FORMS OF LIFE 25 


ers that they belong together. The figs include such 
apparently unlike plants as the rubber tree, the ban- 
yan and a vine-like parasite. In another great group 
the botanists have been obliged to lump together gera- 
niums, flax, oranges, mahogany and castor beans, 
because they are similar in their ways of propagating. 
The scientists have no desire to do queer things; they 
would much prefer to say that rubber trees and milk- 
weeds are alike because of their milky sap; simplicity 
has always been their aim. But nature has made it 
impossible for them to find any simple way of classi- 
fying. It is as if she had strung the most diverse 
forms on one thread of structure, and had then so 
looped and tangled the thread that the botanists are 
taxed to their wits’ ends to straighten it out in any- 
thing like orderly sequence. When a man has labored 
for thirty years at this effort to untangle related 
forms, he comes to think of plant life as a labyrinth, 
and he demands a clue. What will guide him? His 
work would be easier if he could discover that all the 
crisscrossing forms were originally created as distinct 
kinds of organisms, but the opposite conviction is con- 
tinually thrust upon him—namely, that these forms 
are a jungle of variation, that all plant life has for- 
ever been altering in character, putting out changes 
here, there and everywhere. 

The puzzle would not amount to much if a species 
were always a species—if, for example, a certain kind 
of pine tree were everywhere the same. But within 
any species there may be endless variations, some of 
them amounting to striking differences. A grizzly 
bear, for instance, would seem to be very different 
from a cinnamon bear; but grizzlies have been found 
that shade by slight degrees of color and size toward 
cinnamon bears, and a series of cinnamon bears could 
be arranged that shade off in color and size to meet 


26 EVOLUTION FOR JOHN DOE 


the series of grizzlies. No sharp line can be drawn, 
and hence some scientists have called them all one 
species. 

Another illustration of the endless variegation 
within a species is a certain small grass, growing com- 
monly in the United States and Europe, Draba verna; 
when samples of this are gathered from different 
parts of the world, it is found that there are many 
distinct types—no less than two hundred have been 
counted, each of which will breed as true to itself as a 
Baldwin apple or a Boston Bull. Each of these types, 
the so-called ‘‘varieties,’’ might be called a species. 
And any naturalist who cares to cultivate the varieties 
can breed new ones; he can, as it were, watch the 
plant branching out into new forms. So with wheat: 
one acute observer counted in a field no less than 
twenty-three varieties which would, if separated and 
cultivated by themselves, continue to produce the 
twenty-three types of plants. A botanist in Amster- 
dam once counted seven hundred varieties of hya- 
cinths. It is estimated that American florists have 
caused fifty species of irises to branch out into one 
thousand five hundred distinct varieties; that they 
have developed as many forms of roses; and that 
there have been produced in the gardens of the world 
no less than eight thousand varieties of roses. So 
endless are these variations that botanists have no 
power to tabulate them; one of the most famous, the 
Dutchman de Vries, says of hawkweeds, ‘‘Thousands 
of forms may be cultivated side by side in botanical 
gardens, exhibiting undoubted differentiating fea- 
tures, and reproducing themselves truly by seed.”’ 

What shall a naturalist conclude after he has spent 
studious decades in watching these ceaseless fluctua- 
tions of countless forms of plant life? What shall 
he think when he takes stock of this medley of life, 


THE MYRIAD FORMS OF LIFE 27 


this unmapped chaos of contradictions and relation- 
ships? He has no chart or compass until he adopts 
the evolution theory; with it he can always steer a 
course. 

The same remark applies to the zoologist. If men 
had never known of more than five hundred kinds of 
animals, they would not have realized that chaos ex- 
ists and would have laughed at evolution. Down to 
1700 the knowledge of the diversity of life was so 
meager that naturalists did not recognize any mys- 
tery. Even after Linneus had been compiling data 
for thirty years—and no more industrious, capable 
classifier ever lived—he could learn of hardly more 
than four thousand* species; he would never have 
felt impelled to solve a mystery in 1758. But by 1858 
the situation was entirely different; Agassiz then 
calculated that one hundred and thirty thousand spe- 
eies were listed, and many discerning zoologists began 
to fear that they were all at sea. Within thirty years 
from that date the count had more than doubled; and 
twenty-five years later had almost doubled again— 
that is, a conservative count had reached 522,000 spe- 
cies. If by that time (1912) the zoologists had not 
had the aid of the evolution theory, they would have 
been swamped by the mounting billows of species and 
sub-species. 

To say that in 1912 there were listed in scientific 
libraries 522,000 species of animals is like speaking 
of billions of dollars in a public debt—we can not com- 
prehend such a tremendous sum. No more can we 
have a comprehension of the numbers of animals un- 
til we dwell upon a few of the details. One of the 
smallest items illuminates the whole subject striking- 
ly: fifty years ago only thirty species of deep-sea 


_ *Most of the following figures are the estimates of Professor 
H, 8, Pratt of Haverford, in Science, March 22, 1912, 


28 EVOLUTION FOR JOHN DOE 


fishes had been seen; now there have been dredged up 
and accurately described more than one thousand 
species. Linneus, the great father of classification, 
whose fame is still bright, could count only forty-one 
species of worms; there must be 8,000 known to-day. 
We now know of 2,500 kinds of sponges, 16,000 of spi- 
ders, 3,500 of reptiles, 61,000 of mollusks. Collectors 
have penetrated the wildest quarters of the globe, 
have braved the desert heat and the arctic ice, have 
searched the mountains above and the ocean below; 
everywhere they have discovered new species by doz- 
ens and hundreds. Whereas Linneus could count only 
444 kinds of birds, we know of over 13,000. He listed 
only 183 mammals; at present we have accounts of 
some 3,000. 

These figures were compiled by Professor Pratt 
in 1911, and may be ten per cent. under the totals that 
could be reckoned to-day. If any of the figures are 
too high, we may be assured that before many years 
they will be too low; for they are being augmented 
almost daily. L. O. Howard, one of our greatest en- 
tomologists, has said that the number of insects now 
known may ultimately be multiplied by ten. Men who, 
like him, have spent a lifetime amid the rising tide 
of numbers would yawn at our little lists of the hun- 
dreds of thousands; for they do not think in terms of 
arithmetic, but in one term—of a flood of varied life. 

And this flood of life now in the world is only a 
small pool when compared with the ocean of forms 
that have, during the long history of the world, risen 
and flourished and become extinct.* The geologists 
are familiar with limitless reaches of changing life 
that stretch through the millions of years of the geo- 

*The long record of the prehistoric life of the earth, perhaps coy- 


ering five hundred million years, is outlined in Chapter XII. It 
furnishes stronger evidence than the study of the forms now living. 


THE MYRIAD FORMS OF LIFE 29 


logic ages, glimpses of which may be seen in the fos- 
sils. Even the fragments of this ancient history, 
when pieced together in a list, reached, twenty years 
ago, the respectable aggregate of eighty thousand 
species of vanished life. The great naturalist Wallace 
believed that in the whole past history of extinct 
forms of animals there ‘‘must have been thirty or for- 
ty times as many species as are now living.’’ He 
euessed that probably there have been on the earth in 
all its different periods ‘‘many hundred times as 
many species of plants and animals as now exist.’’ 

So boundless, to the gaze of a scientist, is the 
realm of life which we amateurs have tried to skim 
over in one brief chapter. 


CHAPTER IIT 


THE TANGLED WEB OF LIFE 


THERE is nothing baffling about mere numbers of 
species. If the naturalists had never been confronted 
with any problem more puzzling than half a million 
or a hundred million species, they would never have 
been driven to seek out an evolution theory. The pre- 
vious chapter gave several indications of the real 
mystery: the tangle of forms. Only a lifetime of ex- 
perience would give a partial conception of the end- 
less series of kinds that shade gradually into other 
series of kinds. In this chapter we can do no more 
than view, as from an airplane, distantly, a few of the 
thousands of bewildering facts known intimately by 
scientists. 

In the previous chapter we got very little sugges- 
tion of any bewilderment. We saw neat packets of 
‘fone thousand two hundred kinds,’’ of ‘‘three thou- 
sand five hundred kinds,’’ of ‘‘sixty-one thousand 
kinds.’’ The inference was that a biologist could tell 
two distinct species as easily as a stamp collector can 
decide that two bits of printed paper are not dupli- 
cates. 

The fact is just the contrary. Professors Pratt 
and Ganong would be the first to admit that no count 
of species can be made, that their lists represent only 
the roughest approximations to a set of balances of 
opinions. Until a reader understands that statement 
he is not on his way to a comprehension of evolution— 

30 


THE TANGLED WEB OF LIFE 31 


any more than a detective could find a criminal before 
he knew what the crime was. 

What is life? The more we study it, the less able 
we are to give a definition. If an invisible bacterium 
is an individual plant, why is not a white corpuscle in 
our blood an independent animal? And if a white cor- 
puscle is a separate creature, how shall we draw the 
line between it and a cell in our muscles? If these 
self-propagating cells of our flesh are animals, why is 
each self-propagating cell of a leaf not a plant? We 
ean not tell where individual life begins. 

As soon as we pass upward from this doubtful 
region of cells at the basis of all life, we are at a loss 
to know the difference between the lowest plants 
(Protophyta) and the lowest animals (Protozoa). The 
voice of science can only admit that ‘‘no hard-and- 
fast line can be drawn around Protozoa to distinguish 
them from Protophyta.’’ It declares that ‘‘the for- 
mal distinctions between the animal and the vegetable 
kingdoms have vanished, and in their place we have 
an intimate, unbroken continuity.’’ 

So at the very beginning of any examination of the 
world of life it appears that all is confusion. The 
naturalists could never arrive at any understanding 
of this vast tangle until they found some one principle 
that would account for all the variety of the strands 
and for all the interweaving of them. All our obser- 
vation of nature shows that nothing ever happens by 
chance, that every object we see was fashioned by un- 
deviating law. Hence any naturalist in his senses 
must suppose that every least filament in the web, 
every variation of form, every continuous series of 
forms, became what it is by the operation of some 
fixed, unvarying forces. Just as our minds are obliged 
to think that there must be definite causes for rain- 
bows and wireless telegraphy and tides and fires, so 


32 EVOLUTION FOR JOHN DOE 


we take it for granted that the various forms of life 
are not the result of a hodge-podge of unaccountable 
accidents. Much less can any reverent person nowa- 
days credit the idea that a whimsical Creator amused 
Himself and befooled His human children by devising 
a lawless welter of freaks. 

The devout and sensible scientists never tolerated 
such an idea. With one accord they have always as- 
sumed that there is some definite method of creation, 
and they have done their best to discover it. 

After 1700 their efforts were based on a certain 
assumption—a very natural one and very useful. This 
theory was that all animals were arranged on a ‘‘scale 
of nature,’’ from the low and simple forms to the high 
and complex. Hach degree on this scale was a small 
but sudden step upward from one kind—called a 
‘“species’’—to the next higher kind. Thus each spe- 
cies was sharply marked off from the one below and 
the one above; it was a distinct type of life that had 
always been what it now is, and that would never be 
anything else. 

The ‘‘seale of nature’’ hypothesis stood the test 
of experience fairly well in the eighteenth century for 
classifying four thousand species; it still applies after 
a fashion; for the species that we observe in nature 
seem fixed. 

An account of what the word ‘‘species’’ signified in 
1830, and of the controversy about it, is the easiest 
entrance to an understanding of the evolution theory. 
Some readers will wish, first, to see a display of the 
term in its setting in the system of classification that 
has been used for the last two centuries. For their 
convenience the following numbered paragraphs are 
inserted to show the graduated divisions, from large 
to small. This is not a review of technicalities, but is 
an approach to the heart of the subject. 


| 
7 


THE TANGLED WEB OF LIFE 33 


The nature of classification. To begin with, what 
are the scientists about, what is their purpose, when 
they ‘‘elassify’’? They are only doing what we all 
have to do in our private affairs when we arrange or 
sort out a lot of articles that are in confusion. No 
business office can keep five thousand letters in the 
same order in which the postman brought them; they 
must be sorted—that is, classified—alphabetically or 
by their subject-matter. A carpenter must classify 
his tools and nails and screws, else he could never put 
his hand on what he needs; a college must classify its 
students as failing, passing, doing fairly, or doing 
excellently; if the people in a city were not classified 
by names and streets, all general business would come 
to a standstill. So the scientists would be all at sixes 
and sevens unless they carefully classified their huge 
stores of facts. One example will bring this home: 
thirty-five years ago the manuscript of the catalogue 
of plants kept at Kew Gardens in England weighed a 
ton. 

1. Kingdom. A vast labor the classification has 
been, and is still very incomplete. A glimpse at the 
nature of it can be had most easily by noticing how 
the first ancient classifier went to work. He began, 
as any shrewd man would after some observing and 
meditating, by dividing all life into two ‘‘kingdoms,”’ 
vegetable and animal; and the scientists still follow 
this primary division. 

For the first subdivision of animals Aristotle 
found that he could make two great groups, according 
as they had or did not have a backbone. Among those 
with a backbone he naturally made sub-groups of 
those that walk on four legs, those that walk on two 
legs, and those that live in the water. Then his trou- 
bles began; for a man walks on two legs, but is unlike 
all the birds in not being covered with feathers. 


34 EVOLUTION FOR JOHN DOH 


Classification is a task that demands the highest ana- 
lytical skill and patience. To this day the zoologists 
are agitated about the shortcomings and contradic- 
tions of their system of sorting into orderly groups 
all the known kinds of animals. 

2. Phylum. With their elaborate details we have 
no concern, but we do need to know their principal 
terms. In beginning an arrangement of animal life 
they first try to put together in large groups those 
sorts that are similar in some general way—for ex- 
ample, all the backboned animals are grouped to- 
gether into a ‘‘phylum.’’ In another great phylum 
are lumped together all such ‘‘jointed’’ animals as 
insects and lobsters. 

8 Class. Within each huge phylum many subdivi- 
sions must be made—for example all the lobsters and 
crabs and barnacles are put into one ‘‘class,’’ all the 
spiders into a second class, all the insects into a third. 

4, Order. Insects are such a vast horde of dis- 
similar forms that they must be subdivided many 
times before there will be any practical classification ; 
they are sorted into twenty ‘‘orders.’’ One of these 
orders includes all the beetles. 

5. Family. It is clear that classification has only 
begun. The order is divided into great groups called 
‘‘families.’’ The largest family of the beetles, for ex- 
ample, is the snouted weevils. 

6. Genus. This family, like every normal one in 
the plant or animal kingdoms is subdivided into 
groups, each of which is called a ‘‘genus”’ (plural 
genera.) One genus of weevils, named Anthonomus, 
includes many sorts that make a specialty of living in 
buds and pods; its members are spread over the 
whole globe. Classification is always that same op- 
eration of making narrower and narrower divisions 
of groups whose members are somewhat alike, sorting 


THE TANGLED WEB OF LIFE 30 


out those that have closest resemblances into smaller 
and more homogeneous groups, and then again sort- 
ing each smaller group into sections that are most 
alike. | ) 

7. Species. Such a subdivision of a genus is called 
a ‘‘species.’’? A species is the last complete stage of 
the sorting process; it is such a narrow division that 
all the members of it bear a close resemblance to one 
another and can usually mate together; whereas the 
members of two well-defined species can rarely pro- 
duce fertile offspring. Anthonomus contains one 
world-famous species, grandis, which has destroyed 
billions of dollars’ worth of property for the cotton- 
growers—the boll weevil. 

8. Variety. It often happens that within one spe- 
cies there are many somewhat different forms, which 
ean be accurately defined and which breed as true to 
type as distinct species; these are called ‘‘varieties.’’ 

When we consider that such an exhibit of classifi- 
eation, though it extends through eight paragraphs, 
does not represent an outline of the scheme of even 
four thousand animals, we have a faint suggestion of 
the interminable maze of nature, and of the struggle 
which the eighteenth-century naturalists had. 

This struggle centered on one point—on the theory 
that species are unchangeable. The reader must cen- 
ter his attention on the same point, for it is the ap- 
proach to the whole subject. A species, as the eight- 
eenth-century classifiers conceived it, was a certain 
kind of plant or animal that never had been and never 
could be different. Linneus believed that a species 
was an unchanged and unchangeable unit of life. His 
own words were: ‘‘There are just so many species as 
in the beginning the Infinite Being ecreated.’’ 

If this had been true, the course of natural science 
would have been smooth. The zoologists would sim- 


36 HVOLUTION FOR JOHN DOE 


ply have had to detect these eternal kinds of life and 
count them up as astronomers have counted the stars. 
Great was their amazement to discover, long before 
1800, that they could not agree on how to distinguish. 
They all wanted to agree; they all took it for granted 
that agreement would be possible. But with the years 
the disputes increased. Even Linneus had qualms 
when he found how often a dividing line was difficult 
or even impossible to draw. By 1800 a Frenchman (La- 
marck) had denied that such divisions could ever be 
made successfully, because as the stores of facts rap- 
idly increased he saw the tangled web grow ever more 
tangled. He put the case thus in the very year of 
Darwin’s birth, 1809: ‘‘The supposition generally be- 
lieved—that organisms are arranged in ‘species’ that 
are always distinguishable by invariable character- 
istics, and that the existence of these species is as an- 
cient as nature itself—was established at a time when 
men had not observed enough and when the natural 
sciences as yet hardly existed. It is always belied in 
the eyes of those who have seen much, who have long 
attended to nature, and who have studied with profit 
the large and full collections of our Museum.’’ 
_Around the conception of species the battle raged. 
In France and Germany and England there were 
plenty of learned men ready to abandon the idea that 
a species was a fixed fact of nature. But if they had 
done so, where would they have found themselves? 
Floating in a fog of philosophy. It might be all very 
well for a reckless, imaginative Frenchman to aban- 
don facts and speculate about all life as a continuous 
stream of forms that changed into one another. But 
that was to deny their own senses, for they could see 
a multitude of fixed species, and Lamarck could not 
show them one that changed into something else. Why 
should they give the le to their own eyesight? They 
were like Romans who were asked to believe that the © 


THE TANGLED WEB OF LIFE 37 


sun stood still and the earth moved. They decided— 
and quite sensibly—not to follow such vagaries of 
philosophy until some tangible evidence was forth- 
coming. It did not come. No one could find any 
proof for Lamarck’s fancy. By 1850 it was consid- 
ered unscientific and foolish to discuss any evolution 
theory. The fixity theory was more firmly established 
than ever. 

The scientists were, nevertheless, perpetually un- 
easy, at a loss, discordant among themselves. For 
they could not mark the limits of the species that they 
believed in. It was a curious dilemma. If a man be- 
lieved that species were variable, he was beyond the 
pale of realities; but if he believed that species were 
fixed, he could not lay his hand on the realities. Eith- 
er way he was lost and baffled in the tangled maze of 
hving forms. 

‘“What is a species, anyhow?’’ was the constant 
query. Darwin often reveals in his letters what all 
scientists felt, but could not well give vent to in their 
formal publications. He wrote in 1849, when trying 
to classify the barnacles: ‘‘I can not at present tell 
the least which of two species all writers have meant 
by the common Anatifera levis. Literally, not one spe- 
cies is properly defined.’’ In the same year he wrote to 
a great botanist: ‘‘I often feel wearied with the work, 
and can not help sometimes asking myself what is the 
good of spending a week or a fortnight in ascertain- 
ing that certain just perceptible differences blend to- 
gether and constitute varieties and not species... . 
I have just finished two species which possess [1. e., in 
the different works of reference] seven generic and 
twenty-four specific names!’’ Seven years later he 
wrote again: ‘‘In some naturalists’ minds resem- 
blance is everything, and in some resemblance seems 
to go for nothing; in some sterility is an unfailing 
test, but with others it is not worth a farthing. It all 


38 EVOLUTION FOR JOHN DOE 


comes, I believe, from trying to define the undefin- 
able.’’ 

Huxley thus describes a bit of the dialogue when, 
as a young man, he had his first interview with Dar- 
win: ‘‘I expressed my belief in the sharpness of the 
lines of demarcation between natural groups, with all 
the confidence of youth and imperfect knowledge. The 
humorous smile which accompanied his gentle answer, 
that ‘Such is not altogether my view,’ long haunted 
and puzzled me.’’ 

No wonder that Darwin smiled, for he was famil- 
iar with facts like these: ‘‘As soon as these three 
forms, which had previously been ranked as three dis- 
tinct genera, were known to be sometimes: produced 
on the same plant, they were immediately considered 
as varieties; and now I have been able to show that 
they are male, female, and hermaphrodite forms of 
the same species.”’ 

Wallace pictures the situation vividly in this sen- 
tence: ‘‘All students were so impressed with the be- 
lief in the reality and permanence of species, that 
endless labor was bestowed on the attempt to dis- 
tinguish them—a task whose hopelessness may be in- 
ferred from the fact that, even in the well-known 
British flora, one authority describes sixty-two spe- 
cies of brambles and roses, another of equal eminence 
only ten species of the same group.’’ 

The first authority had ‘‘split’’ the roses into six- 
ty-two species; the second had ‘‘lumped’’ them into 
only ten. This case is typical. The same tendency is 
as strong as ever to-day: if a naturalist is keenly in- 
terested in noting slight differences, he will find many 
species and be a ‘‘splitter,’? if his mind works on the 
other tack, he will be a ‘‘lumper.”’ 

In a recent study* of a genus of crickets the an- 


*F, E. Lutz, Carnegie Publication 101. 


THE TANGLED WEB OF LIFE 39 


thor tells us that six species have been commonly de- 
scribed, that one man lumped these into two, that 
another man lumped them into two by a different 
grouping, and that the author thinks there is only 
one species. 

If we should search the ences of the ants, 
as made by all the splitters, we might count six thou- 
sand species; if we took the records of the lumpers 
and selected the lowest list from each, we might have 
no more than two thousand. 

Any amount of similar evidence could be cited to 
show that a species is essentially an opinion. If a 
very careful man makes a prolonged study of a cer- 
tain genus, and if succeeding students think well of 
his judgments, his opinions stand as named species; 
if his judgments do not stand the test, they are set 
aside by the next student. Illustrations like this from 
the Britannica article on wolves can be found very 
frequently in common books of reference: ‘‘These 
differences have given rise to a supposed multiplicity 
of species. . . . But it is doubtful whether these 
should be regarded as more than local varieties.’’ In- 
deed all the efforts of all the authorities to assort 
wolves and dogs and foxes and jackals have failed to 
produce any generally accepted scheme of species. 

A pretty demonstration of the whole species puzzle 
is exhibited in the American Museum of Natural His- 
tory. A cirele of fifteen tiger beetles is so arranged 
that the distinctive markings of one species, shown 
fully in the first specimen, are slightly different in 
the second, somewhat more different in the third, and 
so on, until when we have gone the round we find 
that the fifteenth specimen, next to the first, has the 
markings of another species. 

Truly the works of nature appear as cycles that 
merge into other cycles, and these loops are combined 
in a tangled web of life. 


CHAPTER IV 
THE VARIED MODES OF LIFE 


Wuen I, with my untrained eyes, pay any atten- 
tion to plants, they seem to be very regular, uniform 
things. A buttercup seems like all the other butter- 
cups; an acorn seems to produce the same kind of oak 
that it fell from; a housefly or a June-bug is always 
of the same size and has parents and children that are 
exactly like itself; a sea-gull never mates with a hawk; 
everywhere I go there are a lot of butterecups and 
flies and hawks and ants that are just the same as 
the ones I have seen before; an oyster is never an eel. 
So far as I ever noticed, all forms of life are well sep- 
arated, distinctive, uniform. I never see any puzzle 
or any need of worrying about classifying. 

And so long as I do not see any puzzling irregu- 
larity, I can not have any interest in evolution or take 
any stock mit. Every naturalist would have been as 
indifferent as I am if he had always remained as 
ignorant as | am. No person will see any sense in 
evolution until he knows at least a little bit of the end- 
less confusion and crisscrossing and interlacing of the 
kinds and modes of life of plants and animals. 

So it is time to describe a few of the puzzles that 
every biologist meets with. If you find this chapter 
somewhat bewildering, you are on the road to under- 
standing ; for you can then see, in some slight measure, 
what the scientist’s problem is. This chapter does 
not explain anything. It takes you to a maze of facts 

40 








This 12-inch African antelope (a dik-dik), only a foot high when full-grown, is 
a near relative of the 800-pound Eland antelope. The tropical leaf-hoppers are 
bugs whose heads have developed into great crests as long as the bodies. 





Two strange creatures from Australia. The green phalanger, above, is the only 
known animal that has greenish fur. The duckbill is the only species in its 


family; it has thick brown fur, a bill like a duck, and lays eggs like a reptile. 


THE VARIED MODES OF LIFE 41 


and says, ‘‘Look at this, and this, and this. See what 
the scientist has had to explore and find a clue to. 
Notice that the facts are interlaced and perplexing.’’ 

In this and the following chapters we are going to 
take the course that Darwin’s mind covered in his 
twenty-five years of effort to solve the mystery. It 
is as if we, in an express train, whizzed at a mile a 
minute through the jungles where he had to hack his 
pioneer way foot by foot. As you glance at the few 
dozen illustrations in this chapter, try to imagine what 
they would be like if they were multiplied by a thou- 
sand and if your life depended on working out some 
theory that would bring them all into a neat and 
orderly arrangement. 


I. Groups Are Big and Inttle, Flourishing and Dying 


If I say to a man who has never pondered on the 
mystery of life, ‘‘This yellow-flowered weed belongs 
to a genus (Senecio) in which there are 2,300* spe- 
cies,’? he may think of a greenhouse where there are 
2,300 flower-pots—or he may think of nothing. He 
does not feel that there is any puzzle about it. ‘‘Lots 
of kinds of weeds?’’ he replies. ‘‘I should say so. 
Weeds flourish everywhere.’’ But ask him to imagine 
how a botanist understands the statement. ‘To the 
botanist there is no such thing as the difference be- 
tween a ‘‘weed’’ and a cultivated plant. He knows 
them all alike as plants that have to fight for a living 
in the soil. When he hears of a genus of 2,300 species, 
he recognizes a group that is extraordinarily hardy, 
that has spread over wide reaches of territory, that 
has fought its way to victory in many climates, and 

*Gager, Heredity and Evolution in Plants. Most of the figures 
given in this chapter are taken from older works of reference; hence 


they are generally understated, though in a few instances they will 
be larger than those shown in some recent taxonomic arrangement, 


42 EVOLUTION FOR JOHN DOL 


that has branched into 2,300 different ways of making 
conquests in battles against other plants. He admires 
it as a mighty and successful kind of organism. He 
sees it is an adaptable, ever-varying form that flour- 
ishes like a very fountain of changeable life. 

Show a botanist the opposite kind of picture: 
‘‘Here is a Chinese tree (the gingko) which is a 
separate genus all by itself; there is only one species 
of it.’? Then he is struck as by a sight of a dying 
race. He is puzzled as he contrasts it with a group of 
2,300 species. Why should it remain so stolid and 
meager while another. race goes victoriously forth in 
a myriad of guises? One genus seems to sport in 
lavish, youthful strength ; the other appears to be 
dying. In an orderly universe what should make races 
come and go? 

A zoologist meets the same mysteries of the big 
and the little groups, the flourishing and the dying. 
A genus of squirrels in Borneo and another in India 
have only one species each; of the genus of pigmy 
squirrels there are a few species; of the striped 
ground-squirrels there are more; and of the tree- 
squirrels there are dozens—large and small, gaudy 
and plain—all over the world. Similar contrasts 
could be cited without end. The genus of rabbits is 
everywhere—in the foggy north of Scotland, in Brazil, 
in the Himalayas—overrunning all countries with its 
thirty species; whereas the genus of camels is domes- 
ticated in a small region and has only two species. 

The same contrast of numbers and strength is seen 
in the ‘‘families’”’ of plants and animals. Ordinarily 
a family is a large group embracing several or several 
dozen genera. In the sunflower family there are one 
hundred and fifty genera, and in the great families of 
animals there may be as many. But some forms of 
life are so peculiar that they must be made a family 


THE VARIED MODES OF LIFE 43 


all by themselves; thus there is now living on the earth 
only one genus of the rhinoceros family. 

Those words ‘‘now living on the earth”’ give a hint 
of the depth of the mystery. The study of fossils 
shows that forms have waxed and waned through the 
millions of years of the geologic ages. There used to 
be many genera in the rhinoceros family. A long ac- 
quaintance with this flow and ebb of life arouses a 
suspicion that a large and a small family, a large and 
a small genus, are not permanencies, but temporary 
fluctuations; and such a thought is exciting to any 
scientist who is trying to discover nature’s secret. 
The California genus of sequoias is now limited to two 
species on one strip of coast, though some millions of 
years ago it flourished in many species from ocean to 
ocean. Why should this ancient group have dwindled 
almost to extinction while the genus of pines was in- 
creasing to seventy species that triumphantly made 
their way to every part of the north temperate zone? 

Nor is the mere fact of large and small, flourish- 
ing and dying, the most striking feature of what nat- 
uralists learn. Their curiosity is more aroused when 
they find that a chart of their classifications resembles 
a tree. If a certain order of animals branches into 
three families, two will probably be small side- 
branches and one will be like the continuation of the 
main trunk. If this dominant form divides into 
twelve genera, one genus will be very small, ten will 
be moderate in size, and the twelfth will be the large 
and typical group. It is this dominant twelfth genus 
that will ramify into a hundred species, and most of 
the hundred will show more vitality, be more numer- 
ous, and tend more to split into varieties, than the 
species of the eleven small genera. And of those hun- 
dred more lusty species there will probably be three 
that are decidedly more numerous and common, 


At EVOLUTION FOR JOHN DOH 


spreading into more varieties, than any of the others. 
A botanist expects a map of an order to look like the 
trunk of a tree, which grows upward in a main stem, 
the principal family ; this family continues in the larg- 
est branch, the principal genus; and this genus con- 
tinues upward in a few sub-branches, the principal 
species. 


II, Varied Sizes in One Group 


Among the rattlesnakes there is a species of which 
a full-sized adult is only eighteen inches long; another 
species furnishes specimens four times that length. 
Among the frogs, of the one genus Rana, there is a 
species (goliath, from western Africa) which weighs 
ten times as much as any frog that I ever caught for 
bait. In India there is a rat with a body that is over 
two feet long. The paleontologists have found in the 
family of horses a genus that was only a foot high. In 
a systematic, man-made world the clams would all be 
about three inches long; in the world as it is clams 
range in size from under that standard all the way up 
to gigas, which may be forty-three inches long and 
weigh nearly six hundred pounds. 

There is a parasitic animal so small that it is bare- 
ly visible when shown in a good light against a con- 
trasting background, and another that is two inches 
long, armed and armored in a terrific manner for the 
capture of tarantulas; yet both are wasps. A similar 
case is the pigmy deer, the dikdik of Hast Africa, 
which is only a foot high; it is quite unlike the little 
mouse deer of Asia, but is closely related to the great 
Eland deer which may weigh more than half a ton. 

When a visitor has strolled through a menagerie 
and a museum, he 1s impressed by these freakish vari- 
ations of size; he wonders why nature has sprouted 
out into all these deviations from a standard. 


THE VARIED MODES OF LIFE 45 


III. Varied Developments 


The boy Darwin, like the rest of us, thought that 
a frog was just a frog; it was a leaping land-and- 
water animal that lived and looked like all the other 
frogs. Not until he was dead had the collectors found 
any species that was larger than our American bull- 
frog. How many readers of this book know that some 
frogs never enter the water except to breed; that one 
species burrows for its home; that another lives in 
trees and has a membrane with which it becomes a 
kind of flying frog; that another species builds nests 
among the bushes above the water; that another is 
hairy; that most species have teeth only in the upper 
jaw, while some have teeth in both jaws, and others 
have no teeth; that one species in the Solomon Islands 
has a horn? 

We stay-at-homes, who spend our time with bridge 
and business and novels, never know how, in the most 
uniform and monotonous genus, nature has modeled 
surprising species. She is perfectly varied in the 
most contradictory ways. No person can credit evo- 
lution until he sees something of what naturalists are 
involved in. No uniformity can ever be expected; no 
rule can ever be guaranteed. 

It is a rule, for instance, that animals eat plants 
and that plants draw food from the soil; and that rule 
holds for a hundred thousand species, and the next 
hundred thousand, and the next, and the next. But 
there is an exception. There are one hundred and 
fifty species of plants that eat animals. One, in Geor- 
gia, has hinged leaves that close on a fly, digest him, 
and open for the next fly. Another, in Australia, de- 
velops some of its leaves into cups that entrap insects. 
Our American pitcher-plant, of an entirely different 
order, makes for itself a much more elaborate trap, 
that is always open for insects and digests them by 


46 HVOLUTION FOR JOHN DOK 


dozens. In the Malay Islands there are species of still 
another order that put a lid on their pitchers. 

Rather bewildering, all this, when we consider that 
these similar and very peculiar devices are found in 
different orders of plants on all the continents. A 
fanciful naturalist might guess that since the young- 
est rocks were made, several very different sorts of 
plants had learned to eat meat; for no such fossil 
plant has ever been found. It was a mere fancy, an 
utterly wild and unwelcome one to any steady mind 
in 18380. 

We human beings are apt to suppose that agricul- 
ture and slavery are a pride and a shame peculiar to 
the human race. But go to the ant. There is a tropi- 
eal species which cultivates the fibrous growths of a 
kind of toadstool; they have learned to cut off the 
spore-bearing branches, so as not to let the plant 
breed and destroy itself. Many kinds of ants keep 
plant lice, as a sort of cattle, for their sweet juices. 
Some ants have grown so used to being served by 
enslaved ants that they are powerless to feed them- 
selves and would perish without the servants. 

The more we see of animals, the greater grows our 
wonder at their varied developments. 


IV. Varied Relationships 


Most of us remember the mental shock we received 
when we first learned that whales and porpoises are 
not fishes, but warm-blooded, air-breathing mammals 
that suckle their young on the cold ocean waves and 
that would drown as surely as an elephant if they 
could not breathe air. So we all learned with a little 
start that tree-toads are not toads and that horned 
toads are lizards. Similar contradictions in classifi- 
cation, of a more striking kind, are the stock in trade 
of every zoologist. 


THE VARIED MODES OF LIFE 47 


There is an opossum-like creature in Australia, 
not a foot long, which has a decidedly greenish color 
—the only mammal known which has fur thus tinged. 
In Tasmania there is a creature that looks like a wolf, 
that seems as different from an opossum as a tiger 
does from a rabbit; yet it is allied to the opossums 
and is not a wolf at all. The duckbill, which looks like 
a beaver and is covered with thick fur, has a horny 
bill like a duck and lays eggs. 

Plants furnish many examples of crisscross rela- 
tionships. Staid old peach trees, with only peach-tree 
ancestors, have more than a few times been known to 
send out a sporting branch that bore nectarines. The 
botanist can not draw any boundary line between 
peaches and almonds; for a small, hard, seedling 
peach is very like a green almond in appearance and 
structure; from these inferior peaches ‘‘we may pass 
by small transitions, through clingstones of poor qual- 
ity, to our best and most melting kinds.’’ On the other 
hand an apricot, which seems so like a peach, is by 
some botanists classed in a different genus, is com- 
monly grown on the stocks of plum trees, and—quite 
unlike the peach—will grow true from seeds. 

No matter-of-fact human brain could ever invent 
the freakish relationships that are to be found in 
plant life. Who would have thought of a partnership 
between two classes? A botanist who had dreamed 
that plants ‘‘learned’’ to catch insects might believe 
that his dream was confirmed when he investigated 
lichens: here are four thousand kinds which are com- 
pounds of two different classes of plants, fungi and 
alge. The fungi and alge enter into a very close 
partnership and provide nourishment for each other. 
The truths of botany are stranger than any fiction 
could be. 


48 EVOLUTION FOR JOHN DOH 


V. Varied Ways of Propagating 


Occasionally there is an intelligent person, with 
opinions about evolution, who supposes that winged 
moths eat clothes; he does not know that the moth has 
for a mouth only a delicate tube with which she could 
not injure a cobweb. Yet this same intelligent person 
knows in a general way that there are voracious cat- 
erpillars, with powerful jaws, which spin cocoons, in 
which they become dead-looking pupx, and from 
which they emerge as moths with a slender, sucking 
proboscis in place of the former jaws. Most insects 
go through these three stages of life. A moth or a fly 
comes into its third stage full-sized and usually leads 
a life that is entirely different from its first stage. 

The double life is common among smaller animals, 
in the most extraordinary ways. Many disease-caus- 
ing parasites live their first stage in one animal and 
their second in another. They may live rather harm- 
lessly in spiders or mosquitos or squirrels or pigs; 
then when, by most diverse and remarkable means, 
they reach a second victim—a cow or a person—their 
second stage causes a virulent disease like bubonic 
plague or sleeping-sickness or malaria. Barnacles, 
after living as free-swimming, soft-bodied creatures, 
spend the second and longer part of their life-cycle 
dwelling quietly in a shell. 

Some animals reproduce by throwing off buds; 
some have male and female parts in one organism; 
in some cases the male individual is a mere minute 
parasite; some marine species seem to be male or 
female according to the accidents of their life. Plant 
lice breed for a long series of generations as females 
only, without any pairing; then comes a generation 
that contains males, and there is pairing of the sexes. 
Among the plants are to be seen all manner of com- 
binations: one sex only, two sexes in one plant that 


THE VARIED MODES OF LIFE 49 


mate in that plant, two sexes in each plant that can 
mate only with the sexes of another plant, only one 
sex in each plant. | 

Why should nature, that stern and steadfast moth- 
er, thus toy with ways of propagating that seem so 
wantonly varied? 


VI. Varied Heredity 


We have been taught that like breeds like. We 
know that a grain of mustard seed will produce a 
mustard plant, that an eagle’s egg will yield an eagle. 
Surely, if there is any way in which we might suppose 
that nature is unvaried, it is in this matter of like 
producing like. If I walk through a patch of wild 
roses, they look alike to me; the ones I see in Maine 
seem like the ones in Iowa and California. 

But a florist, who has eyes to see, detects the dif- 
ferences. He knows that roses are very unlike, fluc- 
tuating in size and tint and odor. Put him into a field, 
and he will cull you out a dozen unlike ones, will plant 
their seeds, will cull again from the second generation 
those that are more unlike, will continue for several 
generations, and will then show you a ‘‘new’’ rose, 
such as the sun probably never looked on before. 

To my dull eyes the sheep in a flock are very 
much alike, but a shepherd knows them individually 
and calls them by name. Probably I could not tell 
one ant from another if I studied them under a micro- 
scope, but an Huber knows them apart as if they were 
children of the neighborhood; he names them and 
recognizes their mental peculiarities. Like never does 
beget precisely its like. 

And yet it is obviously the rule of nature that like 
tends to produce like; ordinarily an animal is like its 
parents, as they resembled theirs, and so on back 
through ten generations; we know by specimens in 


50 EVOLUTION FOR JOHN DOE 


our museums that potato-beetles of a hundred genera- 
tions ago are like those that we spray to-day. If 
Huber had lived a thousand years earlier, he would 
have seen similar ants with the same individualities. 
Indeed the tendency to produce similarity seems 
strongly preponderant; for if the florist’s artificially 
selected roses were put back into a state of nature, 
they would soon recur to the ancient type. If cross- 
ings are made between two of our artificial domestic 
breeds of fowl, the offspring may show a strong 
tendency to revert toward the natural form that they 
had several thousand years ago when they were wild 
on the slopes of the Himalayas. Like does tend to 
produce like. 

This contradiction in heredity is an illustration 
of all the paradoxes woven into a web that hid the 
secret of nature from the prying eyes of science. It 
was this woof of contradiction and variation that 
young Darwin had before his eyes when, like Siegfried 
before the wall of flame, he girded himself to pene- 
trate the veil. He indulged in no such heroics about 
matching his intellect against the secret of the ages; 
but, after he had been around the world observing the 
varied forms of life, dedicated himself to the struggle 
in these simple words: ‘‘It occurred to me that some- 
thing might perhaps be made out on this question by 
patiently accumulating and reflecting on all sorts of 
facts. which could possibly have any bearing on it.’’ 
Not till he had spent twenty-two years in accumulat- 
ing did he allow himself to publish. Then his Origin 
of Species opened a wide gate to knowledge, through 
which all men might walk and view a most remark- 
able revelation. 


CHAPTER V, 


THE JUNGLE OF ADAPTATIONS 


In THE last three chapters we have been taking 
glimpses at the mazes of life, and in this chapter we 
shall continue to do the same. There is no explana- 
tion here. We are going to look at a mystery, one at 
which men have always marveled and for which they 
have spun various theories out of their imaginations 
—the devices that enable living creatures to obtain a 
living. 

Every plant and animal has its own way of suc- 
ceeding in its struggle to live, is fitted for getting food 
and competing with its rivals by a peculiar anatomy 
and a particular set of instincts. All such adjustments 
for the fight of life are called ‘‘adaptations.’’? Their 
enormous number and variety, in an endless luxuri- 
ance of competing series of devices, are only feebly 
indicated when likened to a tropical jungle. 

The woodpecker is adapted for preying upon in- 
sects that live under the bark of trees: two of its long 
sharp toes grow backward and two forward, thus 
forming an instrument for grappling the surface of 
a tree; its tail-feathers are spiked to give a purchase 
for the toes and are like a spring to help the hammer- 
ing operations; the bill is a beautiful chisel; the skull 
is, unlike that of any other bird, so contrived that the 
rapid succession of resounding blows on the wood 
can be delivered without racking the head to pieces. 
This bird is adapted for its life-work. It could not 


ol 


O2 EVOLUTION FOR JOHN DOB 


live by wading or by searching for carrion or by div- 
ing in water, but is contrived to be a highly successful 
hammerer. Even a heedless mind is struck by this 
arrangement. Hiven a dull mind naturally asks, 
‘How did it all come about?’’ 

Every child knows of the adaptations of animals 
for fighting and for defense: the rhinoceros is armed 
with terrific horns; the wasp has a most elaborate 
sting and poison gland; a Brazilian eel is equipped 
with an electric battery that can give powerful shocks; 
the skunk and the pinacate beetle emit offensive 
odors; the sword-fish is armed with a combination — 
battering-ram and spear that can pierce the planking ~ 
of ships. Whence came these adaptations? 

Nature-books picture the adaptations of the camel, 
which is fitted for its desert life by the thick soft 
cushions on its feet, by the hump where food is stored, 
by the tanks in its body where water is stored, by its 
power to digest dry shrubs, by its power to close its 
nose when a sandstorm is raging. So complete is the 
adjustment of these parts of his body that the beast 
can carry a rider two hundred and fifty miles across 
the sand in five days without a drink. How were all 
these devices assembled in such a partnership for 
enabling camels to live in the desert? 

The equipment of some animals is so extraordinary 
that a description sounds like a fairy story. There is 
a small fish, living in the utter darkness two miles 
below the surface of the ocean, which makes its own 
light that shines out through port-holes along its 
sides, and which sees through eyes that are perched 
on the end of long stiff tentacles. There are birds 
that hatch out eggs when the temperature is twenty 
below zero. There is a Malay plant with a blossom 
three feet wide which, when it is ready to be fertilized, 
makes an odor like tainted meat, and thus attracts the 











The Tasmanian ‘‘wolf’’ is not a wolf at all, but a marsupial, like the kangaroos. 
The Panda, which looks like a bear, is related to the raccoons. 








The Koala, one of the manv kinds of Australian marsupials, looks like a bear 
and has grasping toes for its life in eucalyptus trees. 


THE JUNGLE OF ADAPTATIONS 53 


flies that will bring the needed pollen from other 
similar plants. These examples are not extreme. 
Stranger ones can be found in books that treat of. the 
wonders of nature—for example Fabre’s accounts of 
insects. 

If you ask a Malay savage why the big red blos- 
som has this queer power of making a bad odor, he 
may tell you a myth of how some angry spirit de- 
signed it. Ask an American business man, who has 
spent his life in trolley-cars and Pullmans, and he 
will say that the blossom was designed that way— 
that’s all there is to it. 

But ask a man who has long been curious about 
the odors of flowers, who knows all about these 
adaptations, and he will shake his head and talk like 
this: ‘‘It’s too much for me. If there were in the 
world only thirty-four odors of flowers, and if each 
were an adaptation peculiar in itself, I could let it go 
at that and bother my head no more about it. But 
the longer a man trains his nose in this study of mine, 
the more he finds out that there is no sharp distinc- 
tion between one smell and the next. No flower has 
any special adaptation of odor, but every one blends 
into its place in the whole long array of all the odors. 

‘It’s like a spectrum of colors—you know, the 
rainbow band that is made when a beam of sunlight 
goes through a prism. If I stick a pin here in the 
band and another pin half an inch farther up, I can 
see the difference between the orange and the yellow 
colors. But if I start at the first pin and move my 
eye along only one thirty-second of an inch at a time, 
I’m not sure whether I can see any difference; the 
change is so gradual and blended. 

‘<That’s the way it is with the flowers. If I made 
up a row of fifty thousand species, starting at the 
bottom with our friend from Malay and putting next 


54 EVOLUTION FOR JOHN DOE 


above him one from Brazil that isn’t quite so offen- 
sive, and on top of that an Abyssinian specimen a 
trifle less rank, and so on, and so on, until I reached 
no odor at all, and then continued my graduated 
scale on up through very slight odors, to violets, and 
up to mignonette, and on up to tuberoses, then I 
should have a continuous spectrum of odors, all grad- 
ing into one another. And that is not the strangest 
fact. The plants in my arrangement for odors would 
not correspond to the botanist’s classification, but 
would cut across his groupings like the shaft of a 
mine through all the orderly layers of rock. The more 
you learn about odors, the more they seem like one 
continuously varying stream of adaptation.’’ 

If you ask a student of birds, ‘‘How were a wood- 
pecker’s adaptations made?’’ he will smile at the ig- 
norance behind the question. To him you are like a 
child who has heard about Franklin’s kite and wants 
an explanation of lightning in words of one syllable. 
‘“Yes,’? he answers, ‘‘the woodpecker’s feet and his 
spiked tail are beautifully designed for life on a tree 
—if you never leave the United States. But in Argen- 
tina and Africa there are woodpeckers, with all this 
equipment, which never light on a tree. Their beau- 
tiful adaptations are utilized for making nests in clay 
banks!”’ 

He pauses to see what effect his sarcasm has pro- 
duced on us. We catch our breath and murmur some- 
thing like, ‘‘Well, we thought that a clear case of 
design like this—’’ 

“Oh, you thought,’’ he interrupts. Now he is irri- 
tated. ‘‘When you learn about some little quaint 
adaptation, you think about it. You think how in- 
geniously nature contrived it. You think that nature 
is a humorous artisan, like a Nuremberg toymaker, 
sitting in her shop and designing animals by fixed 


THE JUNGLE OF ADAPTATIONS 59 


patterns. You ought to be ashamed of yourself. What 
business have you to insult nature and your own com- 
mon sense by talking as if there were only fifty-seven 
varieties of birds, and as if a woodpecker was always 
a woodpecker, and as if you had named a patented, 
machine-made brand of invariable anatomy when you 
say woodpecker.’’ | 

We can’t understand. his earnestness, but we want 
him to keep on and reveal what is in his mind. ‘‘I tell 
you,’’ he continues, his voice rising, ‘‘that you have 
no conception of what you say when you let that word 
woodpecker slip off your tongue. There are three 
hundred species of them, of all sorts, and their adap- 
tations blend into one another so that they seem like a 
crooked current of adjustment, sometimes running 
smoothly and sometimes dammed and thrust out of 
its course; and they crisscross one another so that it 
passes the skill of man to classify the freaks of ad- 
justment. Perhaps you are so observant that you 
know a red flicker from a yellow flicker. What would 
you have done if you had been with me afew years ago 
in Montana when I tried to untangle the mixtures of 
these two strikingly different species? What would 
you guess about adaptations if you found that a cer- 
tain species was all duly fitted out with spikes on its 
tail, but that it couldn’t use them because the tail- 
feathers were too limber? Perhaps you would judge 
that Dame Nature was having some fun at the expense 
of the poor bird, or that she made an error that time. 
You talk about the toes. Why, any quantity of birds, 
quite outside the woodpecker family, have that same 
arrangement of two toes before and two behind; but 
one genus of woodpeckers is not built that way. 
What’s more, some of these ‘yoke-toed’ birds have the 
first and fourth toes turned back, while others have 
the first and second turned back, What do you think 
about those adaptations?”’ 


56 EVOLUTION FOR JOHN DOE 


‘Well, surely, Mr. Bird Man, you can’t blame us 
ordinary people for thinking that any one yellow- 
hammer looks as if it was designed.’’ 

‘‘No, I don’t blame you. I needn’t have talked so 
fiercely. Why, the fact is it used to seem that way to 
me. I was like any savage. When he hooks a big fish, 
he apologizes to it and prays, because he thinks there 
is a spirit in it that will take vengeance on him. He 
thinks that everywhere in nature there is human feel- 
ing, human purpose, human planning and adapting. 
And we civilized people are just like him. When we 
see a bird’s toes adapted for clinging to the bark of 
trees, we ask who did it. We and the savage always 
think of a personality. 

‘¢When an Indian sees the sun moving across the 
heavens, he supposes that it is somebody, and he 
figures out who puts it to bed every night. He sees 
adaptations of plants, and naturally supposes that 
some mind—a little more clever than his own and 
more cruel—planned all the queer devices. He can’t 
think any other way. He has to see all nature revolv- 
ing around his little human brain. But the fact is that 
nature is the big central force, and it is more powerful 
and more remote from our poor thoughts than we can 
conceive. It doesn’t do any petty tinkering in a shop. 
It works in just an opposite way, in a great and 
simple and dignified way.’’ 

‘*(uite a revolution that was in your savage mind, 
Mr. Bird Man. What missionary rescued you?’’ 

‘‘Macts! You know that if you wanted to tell a 
South Sea Islander about the sun, you would first 
have to teach him to count ten, so that he could learn 
to see how many pebbles there are in ten piles of ten 
pebbles each. And when you had trained him to count 
ten thousand, you would then have the long job of 
trying to make him realize what a temperature of 


THE JUNGLE OF ADAPTATIONS of 


five hundred above zero is. You would have to edu- 
eate him gradually in a few simple facts and try to 
give him a picture of some globe that is bigger than 
his island and farther away than across his lagoon. 
HKiven after years of your best training he will find it 
hard to credit a distance so great that the steady 
flight of the swiftest bird would not cross it in a cen- 
tury. How can he ever believe that gravity acts on 
our earth through such a space? I’ll confess I sym- 
pathize with him. The way nature makes adap- 
tations is—well, it’s hard for us humans, on our little 
island of the universe, to take in. You never will take 
it in till you are familiar with the facts, the facts, the 
countless facts.’’ 

‘“You mean things like the humming-bird’s power- 
ful wings and the ostrich’s powerful legs, and so 
forth?’’ 

‘‘No, no. That’s what I don’t mean. Didn’t you 
notice my little parable about teaching the savage to 
understand the sun? You don’t tell him to look at the 
sun. The longer he gazes at it, the blinder he will 
grow. No; you must tell him to look down at the sand 
and learn to put a pebble opposite each toe and say 
‘ten.”? He must learn arithmetic before he can begin 
to hear your story about the big lamp that swings 
overhead. It’s the same with us civilized people if 
we want to know about adaptations. We must begin 
by learning to count a hundred in the simple little 
facts of variation, and then to feel the temperature of 
the struggle for existence, and then peep through the 
telescope of the geological record, and then see some 
experiments with the gravity of embryology. It’s a 
long process to understand how the sun is not de- 
signed to go around the earth. 

‘‘Go ahead for a while with your adaptations. 
They are facts, and you need to know them, But don’t 


58 EVOLUTION FOR JOHN DOE 


injure your dazzled brain by thinking much about 
them at present. After you see a few samples of the 
gorgeous truths, turn back to your pebbles. - It’s the 
only way if you want to understand that the sun of 
adaptation does a revolve around the little globe of 
the human brain.’ 

If we should interview all the zoologists and bats 
anists in the country, we should receive the same kind 
of advice. Let’s skim around the world and gather a 
few impressions of this blinding mystery. 

High in the Andes Mountains, where the streams 
run violently among the boulders, lives a little thrush 
that is adapted for gaining a livelihood in the water. 
Its dense and fibrous feathers keep the body from 
being wet; it clings to stones at the bottom of the cur- 
rent and is able to swim swiftly under water. Yet it 
is otherwise very similar to our song-thrushes. Bats 
in the Mammoth Cave are able to fly, without ever 
brushing the walls, in the remote corridors where the 
darkness is complete. Some fishes and squirrels and 
lizards and squids are fitted with membranes that en- 
able them to glide, almost to fly, through the air. 

Turn where you will, in any corner of the earth, to 
look at any animal, and you will always see some 
beautiful or astonishing contrivance for seizing a liv- 
ing in the fierce competition of nature. How are the 
bees able to save precious time and more precious 
wax by making cells with six sides rather than four? 
Or what steering device enables them to fly so 
straight that they have made a ‘‘bee line’’ a proverb? 
Maeterlinck’s essay on the adaptations of the bee 
makes the Arabian Nights seem flat. The firefly’s 
apparatus is the envy and despair of every lighting 
corporation. 

We could continue to flit thus from case to case 
through all the vast range of the vegetable and animal 


THE JUNGLE OF ADAPTATIONS 59 


kingdoms, and see in every specimen some new adap- 
tation. From an elephant’s trunk to the filament of 
a bacillus every detail of structure would furnish one 
more item for a record so extensive that no one per- 
son’s life is long enough to read it. And even if we 
had time for examples from all parts of the tremen- 
dous catalogue, no such set of mere items would 
picture the principal truth. For when we look at one 
and another and the next, each seems like an independ- 
ent exhibit, complete in itself, neatly stowed onits own 
quiet square foot of space in a dust-proof glass case. 
But in the swirling battle of life it is only a drop in the 
maelstrom, a part of the whole. No plant is adapted 
for itself alone; no animal is detached from the whirl- 
ing struggle of the whole. Here are bacteria and 
flowers and ants that seem adapted for slavery to 
roots and bees and other ants. Elsewhere are poisons 
and claws that seem adapted only to destroy life. 
Kiverywhere in the maze there are plants like the 
mistletoe and animals like the Texas tick that suck 
the food prepared by other plants and animals. These 
are the parasites. In one sense all the higher animals 
are parasites upon plants, for they could not live 
without the food that green plants can form from the 
air and ground. It is estimated that half of all the 
known species of animals are adapted to be parasites 
and can not live in any other way. So adaptation is 
not all a matter of building up elaborate contrivances, 
but is often a case of giving up contrivances and be- 
coming more simple and degraded. 

Adaptation may not be a matter of forms. Often 
it is a set of impulses and instincts that direct animals 
to move to certain flowers or kinds of bark, or to take 
journeys of thousands of miles. Every one knows that 
shad and salmon luxuriate for most of their lives in 
the ocean and then are led by an irresistible impulse 


60 EVOLUTION FOR JOHN DOE 


to run up rivers for spawning. The somewhat similar 
romance of the seals has furnished material to Kip- 
ling. We all know these commonplaces. A more strik- 
ing example of adaptation is the opposite kind of 
migration made by the eels.* These peculiar fish 
emerge from the ocean in their infancy as transparent, 
insignificant bits of ribbon two inches long; the fe- 
males move up the streams and often journey over- 
land; for years—sometimes ten or twenty—they 
continue to grow in size; then back they go to the salt 
water and swim southwest, swim for two years or 
even three, till they reach the deep water south of 
Bermuda; here they spawn; from here the young lar- 
ve head northeast and toil back over the long, long 
weary three thousand miles, growing somewhat small- 
er during the migration; at length they reach the 
friendly fresh water where they can spend a happy 
decade, until they in turn are summoned to return to 
the cold depths, where they spawn and quickly die. 
These lengthy travels are an adaptation, and a very 
successful one; yet to our human way of thinking 
there is something cruel and creepy about it. 

There is the same uncanniness about a whole host 
of migrations in nature. Certain fresh water clams 
give birth to young that attach themselves to the gills 
of a particular kind of fish—not of other kinds—where 
they live as parasites till they are ready to drop off 
and grow up into clams. If our delicate tastes are 
offended by this life-history, we may have one of the 
other sort—for there are all imaginable kinds in this 
jungle of adaptations. Read the pretty story of a 
fiercely spiked yucca, the Spanish bayonet, whose 

*The general nature of the life-history of the eel was correctly 
guessed at sixty years ago, and evidence of deep-sea spawning was 
gathered twenty years ago; the announcement of the discovery of the 
Bermuda spawning region was first made by the Associated Press on 


July 22, 1922, in an account of Doctor Schmidt’s seven-month expe: 
dition from the Copenhagen laboratory on the ship Dana, 


THE JUNGLE OF ADAPTATIONS 61 


stalk of beautiful blossoms is so much admired by 
tourists in the Southwest. This wealth of bloom would 
be impossible and the hardy plant would perish if it 
did not provide food for a certain delicate white moth 
—not any other moth—which brings it pollen from 
other yueeas. And the little moth could never live on 
the dreary plains if it was not fed by the sturdy yucca. 

Such tales of ocean journeys and desert partner- 
ships have a romantic quality that naturally excites 
us to ‘‘think’’ about the origin of the adaptations. 
We had better follow the advice of the bird man and 
not exercise our feeble logic. It is safer just to notice 
the facts. : 

Observe the colors of animals. In many cases the 
splotches and irregular lines of a butterfly’s wings 
are a minute imitation of the leaves on which a but- 
terfly perches. A sharp-eyed collector has often had 
the experience of seeing a specimen suddenly disap- 
pear from sight as if by magic when it lights; so per- 
fectly do its folded wings resemble the surrounding 
foliage. The marking of some insects is like the ap- 
pearance of bark or stem; the stripes of tigers and 
zebras cause them to blend into the landscape, so that 
they can better stalk their prey or escape an enemy. 
All through the animal kingdom are instances of 
different sorts of camouflage that render an animal 
inconspicuous: bears and rabbits and birds are white 
in the northern snow, while most birds and lizards are 
green in tropical forests. Sometimes the most remark- 
able of these ‘‘protective colorings’’ are the least 
spectacular. Sometimes they seem poorly contrived. 
If a speckled, dull-colored bird is protected by its 
markings, why should its breast be a shining white? 
An experiment showed why. An American artist* 

*Abbott H. Thayer. His work was put into a book ealled 


Concealing-Coloration in the Animal Kingdom (1910), by Gerald H. 
Thayer; this yolume is beautifully illustrated with ingenious photos 


62 EVOLUTION FOR JOHN DOK 


painted two sets of dummy birds; to both he gave 
nature’s colors on the back, and to one he gave na- 
ture’s white breast; but to the other set he gave a dull- 
colored breast. Then he placed his two sets of dum- 
mies at a distance and observed them. Those that 
were painted nature’s way, with the light breast, 
blended better with their surroundings and were 
harder to see. Yet even the artist had not expected 
this result, and had a hard time to reason out the 
peculiar problems of light and shade. 

It is needless, even if we had space, to continue 
zigzag journeys from snow to tropics in order to pile 
up the evidence that throughout the whole world of 
life many animals are adapted by their colors for the 
struggle to exist. Such a lengthening of the list would 
be tiresome. But it will be worth while to notice two 
exceptions that prove the rule. (1) Some butterflies 
wear loud colors, seem to advertise themselves to 
hungry birds. This looks like the opposite of adap- 
tation. But in such eases it will be found that the 
butterflies are protected in another way; they are 
for some reason extremely disagreeable to birds, 
which will not eat them. Hence they fly lazily about, 
for they are safer if they advertise themselves as 
an unpalatable kind. The wise birds know better than 
to catch them. (2) Some good-tasting butterflies are 
also conspicuous in their coloring, and also fly lazily 
about. Since they look nearly like the bad-tasting 
ones, and since they don’t mind telling a he about 
themselves, they are saved from the attacks of birds. 
graphs and colored plates, showing that ‘*the most gorgeous costumes 
are, in their way, climaxes of obliterative coloration.’? Who would 
have thought that ‘‘the forest-tones of the peacock ‘melt’ him into 
the scene to a degree past all human analysis’’? The authors show 
how Wallace’s notions of coloration were partial and mistaken, but 
they out-Wallace him in proving the universality of these adaptations 
for protection. See also Theodore Roosevelt’s Revealing and Conceal- 


ing Coloration in the Birds and Mammals, Bulletin of the American 
Museum of Natural History, 1911, 


f 


THE JUNGLE OF ADAPTATIONS 63 


And yet, for all their apparent resemblance, they be- 
lon® to quite another family and are as different from 
the bad-tasting kind in structure and habits as peli- 
cans are from eagles. What is more—incredible as 
_ the fact may seem—one species of good-tasting but- 
terfly, within the limits of one country, has been found 
to imitate the appearance of three different kinds of 
bad-tasting ones. 

At this point our uneasy powers of logic again 
throb for action, but the next set of facts shows the 
futility of logic. Among some species of good-tasting 
butterflies only the females are colored like the bad- 
tasting species; the poor males have been left most 
eruelly unprotected. It is only certain species of these 
good-tasting butterflies that resemble the bad-tasting 
ones; other species are left without any imitative col- 
oring. In a common genus of the United States only 
one species is disguised; all the others have to live | 
without protection. 

Descriptions of all the freakish ins and outs of 
insect mimicry would fill a big book. Some beetles 
resemble other beetles, while some resemble bees. 
Wing-covers are extended, antenne knobbed, and legs 
made hairy in the most comical ways, so that the nor- 
mal structure can be detected only upon careful ex- 
amination. A cricket has been found that—unlike all 
its relatives—has the outward appearance of an ar- 
mored beetle, and another cricket wears the garb of 
the very wasp that preys upon it. Shall we argue that 
nature first designed the wasp and then mocked it by 
designing a disguise for its prey? We have all seen 
fierce-looking flies that masquerade as hornets and 
that have a body motion like a hornet. Is nature fav- 
oring these flies with her funny contrivance, or is she 
cruel to all the other flies? Some flies resemble bees 
and daringly invade hives to lay eggs; the larve that 


64 EVOLUTION FOR JOHN DOE 


hatch from these will eat up the young bees. Why 
should nature design such a crafty deceit of the bees, 
or why should she leave the poor things so witless as 
not to recognize the murderers? We could ‘‘think’’ 
that she played the same scurvy trick on some ants 
in Brazil, reasoning that when she made a little man- 
tis in exact imitation of them and sent him among 
them to kill them, she was determined to punish them 
for wearing the clothes she had given them. 

We have had enough examples of how sensible the 
advice of the bird man was. If more proof were 
needed, we could reprint pages of Wallace’s chapter 
on Mimicry in his Natural Selection, telling how a 
caterpillar resembles a snake in color and pose—and 
many such oddities. 

Adaptation is a bigger and more fascinating sub- 
ject than any mere list of curiosities. It includes all 
those marvels of architecture that can be seen in whole 
groups of animals. We had best not describe the most 
astonishing of these, for they might give an impres- 
sion of exaggeration. We may pass by such wonders 
as those of blood and digestion, which are largely 
beyond our ken, and speak of some bit of mere anat- 
omy. 

Look at a feather. We can see it is adapted for 
propelling a bird through the air in search of a living. 
Have you ever examined a feather or thought any- 
thing about it? Man has not made any material so 
hght and stout and elastic as the thin horny quill. We 
say familiarly ‘‘as light as a feather,’’ but we might 
better say ‘‘such a miracle as a feather.’’ For its 
make-up is admirable beyond all description. From 
each side of the central shaft branch hundreds of 
miniature feathers, the barbs, each of which sends out 
its hundreds of branches, the barbules. These are 
airy plates, each of which is delicately and accurately 


THE JUNGLE OF ADAPTATIONS 65 


frayed into hooks on the forward edge, delicately and 
accurately grooved on the rear edge. Hach barbule 
fits its hook neatly and firmly into the barbule in 
front of it and holds in its grooves the hooks of the 
barbule behind it. So precisely are these couplings 
made that the surface of a wing is as smooth as paper. 
One student of birds counted the parts of a crane’s 
feather; there were over one thousand three hundred 
barbs on one side, each of which branched into six 
hundred barbules—eight hundred thousand adapta- 
tions on one side of ‘‘just a feather.’’?’ And then the 
wonder has only begun. The different feathers on a 
bird are not all duplicates of one pattern; there are 
all lengths, all degrees of fineness from plume to 
down; there is a whole range of uses—for flight, for 
water-proofing, for warmth. When we have counted 
the parts of one feather and multiplied by the number 
of thousands of feathers on some heron that wades 
for shiners in a remote Adirondack lake, we begin to 
get a glimpse of what adaptation means in nature. 
We often speak of these adjustments as ‘‘perfect.’’ 
So they may seem. If we examine the sole of a fly’s 
foot, noting the suckers and hairs that enable it to 
run about on a smooth ceiling, we are excusable for 
exclaiming, ‘‘A perfect contrivance!’’ But there are 
many exquisite structures at which we can only guess. 
We can, for example, see the remains of a certain 
microscopic plant which goes on propagating in quad- 
rilions age after age and dropping its tiny shells to 
the bottom of the lake in which it lives; we can see 
that the markings on these shells—125,000 to the inch 
—are exactly equal and spaced at exactly equal dis- 
tances from one another; they are so infinitesimally 
precise that they prove man’s most skilfully made 
lenses to be clumsily inaccurate. Such perfection of 
structure could not have been an accident; yet we do 


66 EVOLUTION FOR JOHN DOE 


not know the use of it. We can only look with awe 
at these products of an unseen force of adaptation. 

There are some features of plants which appear to 
serve no purpose whatever. In other cases—as when 
potatoes grow on stalks in the air—the machinery of 
the plant seems out of order. In many ways a long 
familiarity with plants causes a botanist to feel that 
adaptation is a means of ‘‘doing well enough’’ or is 
‘‘a chance product of the play of forces’’—and so is 
far from perfect. 

An adaptation is often successful only for a time, 
in certain peculiar conditions. For instance, if a nat- 
uralist could have studied animals some millions of 
years ago, he might have called a ‘‘Thunder Lizard’’ 
perfect for its surroundings, because the bones a foot 
thick were such superb engineering for a cantilever 
skeleton that was sixty feet long. But when the cli- 
mate changed, the Thunderer proved very, very im- 
perfect, and his race died out. The record of the 
fossils is one long roll of creatures that were ‘‘admir- 
able’’ and ‘‘perfect’’ adaptations for one way of life, 
but that perished because they were unable to live in 
competition with better forms. No doubt the old 
saber-tooth tiger was king of the beasts by virtue of 
the formidable weapons in his upper jaws, and no 
doubt the Irish elk was justly proud of his hundred- 
pound antlers, the hugest the world ever saw; but 
both adaptations were good for only one set of condi- 
tions; when the conditions changed, the adaptations 
brought their owners to destruction. 

Many and many an adjustment that we see about 
us now is only partly successful. It appears that 
the bee is just well enough adapted to thrive, and no 
more: her instinct drives her to toil with such in- 
cessant vim that she dies after a few days of work 
at the height of the season; in many ways she is 


THE JUNGLE OF ADAPTATIONS 67 


stupid. The teeth of a beaver are certainly a success- 
ful adaptation in one way, but if they are not kept 
worn down by constant gnawing, they grow so long 
that they kill the beaver; that hardly seems a perfect 
arrangement. Flies are a good example of successful 
adaptation, yet they are so imperfect that they are 
subject to the ravages of a plague of fungus. Silk- 
worms and elm trees have been threatened with ex- 
tinction. We may properly speak of an eye as a most 
marvelous adjustment, may call it perfect, but in re- 
ality it is far below what an ideal instrument might 
be; one great student of optics said it was so inexact 
and imperfect that we might almost suppose nature 
was trying to keep us from knowing what the world 
really looks like. The way in which the leaves of 
plants can adjust their ‘‘breathing’’ to changes of 
temperature and moisture is a notable case of adapta- 
tion; yet it is so far from perfect that when a leaf 
opens its pores to let gases in and out, it may allow 
too much water to escape, and thus sometimes com- 
mits suicide. Adaptations are known to be imperfect, 
to succeed one time and fail another. 

The botanist, as he studies the ways in which flow- 
ers are adjusted for bees, can not escape the feeling 
that all these beautiful and intricate devices are tem- 
porary, that flowers and bees have not always had 
this curious partnership. And the geologist says, 
‘You are right. Only a little while ago, geologically 
speaking, there were no bees and no bright flowers 
in the world.’’ So the botanist finds a double fas- 
cination in his study of the ways in which flowers 
are decked in colors and perfumed, their sweetmeats 
displayed, their barriers and passageways rigged up, 
their stamens and pistils set in order—always in such 
a manner that some bee or moth or humming-bird is 
tricked into carrying pollen. Every colored flower is 


68 EVOLUTION FOR JOHN DOE 


a fit subject for a long essay on adaptation: it must 
have pollen from some distant blossom, and must have 
its own pollen carried to another blossom; this con- 
’ veying is done for some plants by the wind—and these 
have no colors or sweets; but plants which depend on 
insects lure them and pay them. Here is Darwin’s 
description of how one orchid operates: 

‘‘This orchid has part of its lower lip hollowed out 
into a great bucket, into which drops of almost pure 
water continually fall from two secreting horns which 
stand above it; and when the bucket is half full, the 
water overflows by a spout on one side. The basal 
part of the lip stands over the bucket, and is itself 
hollowed out into a sort of chamber with two side 
entrances; within this chamber there are curious 
fleshy ridges. The most ingenious man, if he had 
not witnessed what takes place, could never have 
imagined what purposes all these parts serve. But 
Dr. Criiger saw crowds of large humble-bees visit- 
ing the gigantic flowers of this orchid, not in order 
{o suck nectar, but to gnaw off the ridges within the 
chamber above the bucket; in doing this they frequent- 
ly pushed each other into the bucket, and their wings 
being thus wetted, they could not fly away, but were 
compelled to crawl out through the passage formed 
by the spout or overflow. Dr. Crtiger saw a ‘con- 
tinual procession’ of bees thus crawling out of their 
involuntary bath. The passage is narrow, and is 
roofed over by the column, so that a bee, in forcing its 
way out, first rubs its back against the viscid stigma 
and then against the viscid glands of the pollen-masses. 
The pollen-masses are thus glued to the back of the 
bee which first happens to crawl out through the pas- 
sage of a lately expanded flower and are thus carried 
away. When the bee, thus provided, flies to another 
flower, or to the same flower a second time, and is 





Adaptation on the rocks of Nahant—from the barnacles at the top, which are 
able to live much of the time in the air, to the sponges at the bottom, which are 
fitted for being constantly covered by water. 





A large model which shows to a slight extent how the malaria mosquito is 
adapted for its way of living. Even if this model were magnified a hundred 
times, we could see only dimly some of the larger adaptations. 


THE JUNGLE OF ADAPTATIONS 69 


pushed by its comrades into the bucket and then 
crawls out by the passage, the pollen-mass necessarily 
comes first into contact with the viscid stigma, and 
adheres to it, and the flower is fertilized.’’ 

From a picture of that sort we should like to go 
on through the gallery of adaptations, seeing how one 
plant spreads all its flowers and leaves in a space no 
larger than a pinhead; how leaves and roots, when 
they first emerge from the seed, do not grow in the 
wrong direction; how plants blossom late or early, 
and thus avoid some competition; how the tips of 
roots are highly organized mechanisms for pushing 
through stiff soil and forcing water, with substances 
in solution, up to the stem; how tumble-weeds 
bowl over the prairies and scatter their seeds, and 
cockleburs hook themselves to cattle by the most del- 
icate barbs, and milkweed pods send out their seeds 
in the finest silky parachute; how sap is pumped up 
three hundred feet in tree-trunks by a process that 
no physicist has yet explained. But there is not space 
in this volume to do more than hint at the endless 
variety of ways in which plants are adjusted to live. 

A set of pictures of ingenious mechanisms is all 
very well for entertainment, but is apt to blind us to 
the far more marvelous facts of adaptation that are 
to be seen in the anatomy of any plant. If we, like a 
child, are satisfied with shouting, ‘‘Oh, see the pretty 
seed sail!’’ we shall forget the deeper wonders of 
the structure of one of those gossamer threads that 
float the seed along. Every slightest shred of such 
material passes understanding. 

Here at our feet is a bunch of clover. As you look 
at it indifferently, you are, in comparison, like some 
giant a million miles tall who is looking at our earth. 
If his eyes were no sharper than ours, he could not 
detect Chicago or the height of the Andes. So, if we 


70 EVOLUTION FOR JOHN DOE 


wish to see anything of a clover leaf, we must make 
ourselves small. We must reduce ourselves to the di- 
mensions of a medium-sized microbe—to the height, 
say, of one-ten-thousandth of an inch, while we retain 
the vision and the mental powers of a man.* Permit 
yourself to be thus minimized while we take an excur- 
sion for a few paragraphs into this clover leaf that 
nods in the breeze—just an ordinary, matter-of-fact, 
humdrum leaf that is carrying on its existence by the 
use of certain commonplace adjustments to soil and 
light. Shrink yourself gradually, and thus avoid too 
great a shock. First you are two inches in height—four 
times as tall as the width of the leaf, which now looms 
before you a spiny, big-ribbed affair, glowing with 
life.. Then you are reduced to a tenth of an inch; you 
cling to the edge of the leaf, which seems thirty feet 
broad, and you feel a vertigo asa breath of air swings 
you through an are of twenty feet. Become ten times 
smaller still; the leaf is a hundred yards broad, and 
the little fuzzy hairs appear as spiny trees fifteen feet 
high that glisten against the background of billowy 
green. If you submit to another similar reduction, 
the opposite edge of the leaf will be more than half a 
mile away, lost to view beyond the swell of the sur- 
face. One last reduction, and here we are—two mi- 
crobic pygmies at the edge of a leaf nearly six miles 
wide. We find ourselves perched on a ridge that is 
as rugged and jagged as an arm of a volcanic moun- 
tain. Indeed we are on a more perilous footing than 
those tourists in the Yellowstone Park who motor 
over a rocky knife-edge that slopes steeply down three 

- *I have tried to earry out Ganong’s hints: ‘‘The student can 
see photosynthesis proceeding as clearly in imagination as he could 
with the physical eye were he sufficiently small to wander at will 
through the intercellular passages, and view the operations through the 
erystalline walls of the cells’’; and ‘‘the ordinary stoma [pore], when 


‘open, presents to a molecule of water an exit as great as a passage 
seven miles wide appears to a man.’’ 


THE JUNGLE OF ADAPTATIONS 71 


thousand feet on either side; for our leaf is in its 
fleshiest part less than a thousand feet thick. 

Beneath us we feel the throb of the mighty proto- 
plasmic engines; we have glimpses of great streams 
coursing beneath the shining water-proof surface of 
the top, which undulates for two and a half miles to 
the cafion that is over the midrib. All this plateau is 
covered by a forest of the white spines that rise like 
giant masts of crystal fifteen hundred feet above the 
network of blackish veins. 

Before we venture into the terrifying interior of 
this monstrous place, be assured that we are not play- 
ing with a fantasia. Small as we have made ourselves, 
we are not nearly small enough to penetrate the last 
secrets of a leaf. Our vision is still far too coarse to 
see even the most puffed-out molecule of starch or 
sugar, which would be to our gross microbic eyes only 
one-two-hundred-fiftieth of an inch in diameter. No, 
small as we are, we have descended only to those lim- 
its that a microscope can reach, and are still like 
great blinking monsters before the ultimate adapta- 
tions. 

We are altogether too large to enter through the 
upper side of the leaf; no space there would admit 
a finger. We peer along the under side. About a hun- 
dred yards away is a hole that looks promising. For- 
tunately there is a thousand-foot spine, rooted beyond 
the opening and growing across it, close along the 
under surface, that offers us a rough bridge. We 
scramble along on this huge sparkling log, below the 
under surface of the leaf, till we are beneath the 
mouth of a cave. At first we are almost blown off 
by a blast of oxygen that is rushing out, and then are 
almost sucked in by a whirling current of air. At 
the edge of these currents we find a place where we 
may swing ourselves by our hands up to an oval aper- 


(2 HVOLUTION FOR JOHN DOK 


ture that is heaving in an alarming manner. We can 
feel the surge of sap in the bulging guard-cells, which 
sway the wall of the cavernous mouth to and fro; they 
might quickly swell across the opening and crush us. 
Luckily at just this moment they are slowly drawing 
apart. 

We venture between them when the opening be- 
comes five feet wide. We find ourselves at the bottom 
of a funnel whose wall rises steep and slippery forty 
feet above us. Up this we clamber. Here at last is 
quiet and security, for we are in an open space some 
fifty feet wide and a hundred high, whose sides are 
composed of a dozen or more irregular blocks. Imag- 
ine some houses, with elastic walls, wedged tightly but 
not accurately together to enclose a great chamber, 
and you will have an idea of the surroundings that 
close us in. The walls of these houses are six inches 
thick, but so nearly transparent that we can make out 
fairly well what lies behind them—green globes and 
disks, ten feet or more in diameter, that are suspended 
in a sort of thin syrup, and that are slightly in motion. 
The ‘‘houses’’ are the cells. The green globes are the 
machines that manufacture sugar—and sugar-making 
is the chief business of a leaf. In the course of a 
summer it will produce enough sweet food to form a 
layer half a mile deep over its whole surface. 

If we wish to explore, the way lies open above. 
We had best take our bearings, so that we shall not 
get lost in the galleries that ramify among the big 
eells. Our forty-foot climb up into this chamber was 
through the under surface of the leaf; we are now in 
its soft interior. Above us lies the thickness of the 
leaf—perhaps six hundred feet—which is packed 
nearly full of the house-like blocks, through whose 
walls we have been looking. These are the green cells; 
half a dozen layers of them are between us and the 


THE JUNGLE OF ADAPTATIONS 73 


top surface of the leaf; all around us they stretch, out 
to the very edges—a million or more of them. We 
are going to climb around through the air passages 
that twist and wind in every direction among the cells, 
and we must keep good track of our directions, or 
we shall never find our way back. 

Through the air-passages we poke our way be- 
tween the pulsing walls of the cells and mount toward 
the upper side of the leaf. The cells become more 
narrow, more close-packed, more green, until, when 
we have struggled upward four hundred feet, we come 
to the base of a close array of them that are much 
longer, wedged tight together, like so many flexible 
boxes, reaching to the upper surface. They deserve 
their name of the ‘‘palisade’’ cells. At one point 
We can squeeze another hundred feet through an air- 
channel, but here it ends, and we must stop. 

Familiarity with these more active upper cells 
shows somewhat of their inside. The sugar-making 
disks, smaller and flatter here, float in a liquid. But 
the liquid is only the lining of the cell. All the in- 
terior is filled tight with sap, which holds the syrup 
against the wall. 

We never tire of watching this syrup, viewing it 
as if through the glass of an aquarium. It is in con- 
stant motion, sometimes swirling by a mile* a minute, 
sometimes busied with little whirlpools; now it is of 
the faintest green color, and now yellowish; here it is 
a thin, translucent jelly, and there is filled with fibers 
and rods, globes and crystals. It is protoplasm. It 
is life. Whatever other wonders we see in a leaf are 
explainable to some degree by a chemist, but man has 
hardly spoken the first syllable that shall help to 
interpret protoplasm. When we have begun to under- 


*Actually four miles—if a mile is reckomed as nine hundred times 
our microbic height. 


(4 EVOLUTION FOR JOHN DOK 


stand it, we shall have begun to understand life—not 
before. It is as different from mere sugar as a man 
is from a stone. If you grant a biologist just one cell 
full of this protoplasm, he can imagine that from it 
came all the classes of life; without it he can not 
account for the beginning of life; all inorganic matter, 
be it ever so complex, is on one side of a great gulf, 
and protoplasm is on the other side. 

What a purblind, witless thing is man when he 
encounters a leaf! 

As we continue to explore, we are overpowered 
with the complexities that surround us, of which we 
can gain hardly any knowledge. Here is a strange 
cell that contains, as if it were a show-case in a muse- 
um, a glittering, spiked crystal five feet in diameter. 
We are bewildered by the currents all about us: air 
circulating everywhere, water pumped through tubes, 
sugar carried out for transportation to the roots that 
need the food, sugar transformed to starch and back 
again to sugar. 

And all these operations are simple eon aanag Mic 
the other functions of a leaf. Not all of man’s fac- 
tories and laboratories can equal the refinement of 
the varied processes that go on every minute here. 
There are special cells to produce the water-proofing 
for the outside of the top; others make cellulose and 
build the walls of veins with it; there are the guard 
cells that regulate the intake and outgo at the pores. 
A leaf compounds the most delicately adjusted kinds 
of intricate carbohydrates and proteins, of oils and 
fats and coloring-matters and alkaloids and digestive 
fluids and acids, and many products that are quite 
beyond detection. 

Suppose that the human mind could partly grasp 
the possibility of assembling all these activities in a 
soft plate half an inch wide and one-hundredth of an 


THE JUNGLE OF ADAPTATIONS 15 


inch thick; the mind would only have begun its jour- 
ney of understanding. What regulates and directs 
the whole organization? Where is the ‘‘nerve cen- 
ter’’ that tells ten thousand pores to open five per 
cent. wider because the temperature has changed? 
Where is the mechanism that controls the turning of 
leaves for a better spread to the sun? Whence issue 
all the uncountable thousands of orders every hour 
to the hundreds of thousands of cells, telling them 
when to work and when to desist? What engineer so 
directs the currents that in every least vein the sugar 
is floated toward the stem and water is propelled in 
the opposite direction? We weary of a mere re- 
hearsal of a mere part of these orders for work. 
Our excursion is over. Now we may enlarge our- 
selves to our normal size and be again the blind and 
massive monsters who can see nothing in a leaf. We 
look down at the hall of wonders where we spent such 
an adventurous hour—at a mere clover leaf bobbing 
in the wind. Somehow our minds are no longer in- 
terested in ‘‘thinking’’ about adaptations. For all 
this assemblage of intricate powers is but a fragment 
at the outer edge of a tenfold more marvelous assem- 
blage—a whole plant, whose leaves and roots work 
as one body for producing flowers that can summon 
the bees to aid them in producing seeds. And a seed 
is the supernal wonder, for within its narrow case are 
enclosed all the adaptations of a mature plant, every 
detail of every kind of roots and sap-ducts and 
stems and sweet scent and future seeds. Here with- 
in a seed is a universe which appals the mind as muck 
as the farthest reach of the starry spaces, and which 
is farther from our comprehension. Here centers the 
whole of life. All adaptations are but means to this 
end—that the power to live shall be passed from an 
individual to its offspring. If we would know the 





76 EVOLUTION FOR JOHN DOK 


little that the scientists can learn about the secret, we 
must lay aside all our gross and savage supersti- 
tions as to how nature might work if she were a mor- 
tal. We must realize that nature is not revolving 
around our human ways of thought to be a convenient 
servant to us, but that her secret is the remote force 
about which our petty minds swing in their unknown 
void. 

Probably we can never grasp the secret, any more 
than an astronomer expects ever to fly to the sun. But 
we can observe it to some extent. We can see a little 
way into the material facts of life, and can learn how 
great is the distance from the heedless disregard of 
a leaf to the central fact of adaptation. 


CHAPTER VI 
THE STRUGGLE FOR EXISTENCE 


Tis chapter is the first of four steps in describ- 
ing evolution. It is a description of the fundamental 
fact—never understood a century ago—that the life 
of every plant and animal is a struggle in a fierce 
competition for a chance to exist and propagate. If 
nature had caused all her creatures to live by a pol- 
icy of ‘‘give the weak ones a chance,’’ there never 
would have been any development of such adaptations 
as were described in the previous chapter. 

Karly in every man’s life there comes a time when 
he hears the story of the blacksmith who offered to 
shoe a farmer’s horse for some grains of wheat— 
thus: one grain for the first nail, two for the second, 
four for the third, and so on. Of course the farmer 
was pleased with such a price. The driving of the 
fifth nail cost him only sixteen grains, and the total 
wages for putting on the first shoe were only two hun- 
dred fifty-five grains. The farmer kept tally: two 
hundred fifty-six grains for the ninth nail, five hun- 
dred twelve for the tenth, one thousand twenty-four 
for the eleventh. He was amused, and the more so 
because his wheat was small; it took five hundred of 
the grains to fill a cubic inch, and a million of them 
to make a bushel. The last nail of the second shoe 
cost him not much over a quart. He lighted his pipe 
and smoked contentedly, reflecting that he was pay- 
ing hardly anything for the labor and nothing for the 
material. 


(us 


78 EVOLUTION FOR JOHN DOE 


The trouble began while the third shoe was going 
on; the twentieth nail cost 524,288 grains—half a 
bushel; the twenty-first a bushel, the twenty-second 
two bushels, the twenty-third more than four bushels; 
the total for the third shoe amounted to sixteen bush- 
els. The thirty-first nail cost over a thousand bush- 
els; the total price for the job was four thousand two 
hundred fifty-six bushels. 

When we tell this story to children, we are amused 
at their skepticism and pleased with our effort to 
show them the difference between adding two and 
multiplying by two. We do not realize that we need 
the lesson for ourselves when we consider successive 
generations of animals. The rate of increase is not 
found by adding to their number each time, but by 
multiplying. Most animals tend to increase by a fac- 
tor larger than two, and it does not require a long 
stretch of years to include thirty-two generations. 
Even a seasoned mathematician is rather startled 
when he figures the number of descendants that one 
pair may produce in no long while. 

The largest and most slow-breeding kind can fur- 
nish amazement if we grant them a few centuries. 
Suppose that the average pair of elephants produces 
only four children that live to have grandchildren, 
and suppose that there are only three generations in 
each century, and suppose that the parents die as soon 
as they have brought up their last child. Under these 
conditions one pair will have sixteen great-grandchil- 
dren in the world after a century, one hundred twen- 
ty-eight descendants after two centuries, and one 
thousand twenty-four after three centuries. The rate 
of increase may seem as insignificant as it did to the 
guileless farmer. But in five hundred years there 
will be sixty-six thousand descendants; in six hun- 
dred years there will be over half a million, and after 


THR STRUGGLE FOR EXISTENCE 79 


another century over four million. Now the numbers 
roll up. In the thirty-second generation of descend- 
ants there will be eight billion five hundred million— 
that is, five times the human population of the globe. 
After seven more centuries of increase there would 
not be standing room for the elephants if they were 
packed closely on every acre of land surface from pole 
to pole. Does seventeen centuries seem a long while? 
It is not the thousandth part of the centuries during 
which elephants have been breeding on our earth. 

There is no trick in this reckoning; the figures do 
not lie; they give a conservative estimate of the way 
elephants actually would have increased if they had 
had a chance. We know as a matter of history that a 
few horses, left by the Spanish conquerors of Mexico 
to run wild, must have increased on our western 
plains for a century or more at a rate that doubled 
their numbers in each generation. 

As soon as we deal with smailer and more short- 
lived animals, the normal rate of increase is pro- 
digious. In 1860 a few rabbits were carefully conveyed 
to Australia and tenderly nourished there with the 
hope that a few of them might be able to live and 
propagate. Never was a hope more abundantly ful- 
filled. So rapidly did they multiply that within twen- 
ty years they were a pest; rabbit-drives had to be 
organized, and such heaps of the animals were slaugh- 
tered that it was difficult to dispose of the carcasses. 
A fence of wire mesh was run clear across the con- 
tinent in order to head off this prairie-fire of life. 

Any animal that bears several young in one litter 
and breeds several times a year can soon make a 
counting-machine weary. In two years of the World 
War the rats multiplied enormously along the battle 
line—amid all the destruction of artillery and poison 
gas, in spite of the utmost efforts to hold them in 


80 EVOLUTION FOR JOHN DOE 


check. Against the unremitting warfare of man, rats 
have always increased wherever there is food. One 
estimate of their fecundity in England is that, even 
if ninety-five per cent. of them died without breeding, 
they could quadruple their numbers in a year. If they 
had food and room, and were not opposed, their skins 
could make a carpet for the earth in a few decades. 
Some similar computation would be true of any 
animal that is normally adapted to hold its own in 
the world. It is fitted to increase in swarms, and ever 
multiplying swarms; and whenever it has opportunity, 
it infallibly lives up to the predictions about its fer- 
tility, actually does propagate in overwhelming num- 
bers. The English sparrow was brought to our shores 
in 1851 and promptly set to work producing every 
season several large broods. Within twenty years 
it had become more numerous than any native bird. 
The point of this story is not that a certain sparrow 
is an undesirable citizen, but that any bird in a 
favorable environment will unfailingly produce as- 
tounding numbers in a few years. A very moderate 
estimate will show that a pair of blackbirds could 
easily become ten millions in ten years, and that many 
ordinary birds could have two billions of descendants 
in fifteen years—would unquestionably have that many 
in favorable surroundings. When the Ohio Valley 
was being settled, the pigeons used to be seen in such 
numbers that we gasp as we read the naturalist Wil- 
son’s account of what he once saw in Kentucky. ‘‘ They 
were flying with great steadiness and rapidity, at a 
height beyond gunshot, in several deep strata. From 
right to left, as far as the eye could reach, the breadth 
of this vast procession extended, seeming everywhere 
equally crowded. It was then half past one. About 
four o’clock in the afternoon the living torrent above 
my head seemed as numerous and extensive as ever.” 


THE STRUGGLE FOR EXISTENCE 81 


Wilson reckoned that in this one ‘‘torrent’’ there 
were two billion pigeons; and this was ‘‘only one of 
several aggregates known to exist in various parts of 
the United States.’’ Yet these pigeons hatched only 
two eggs at a time. 

Every form of plant or animal life has some simi- 
lar ability to multiply its numbers. Until we hear 
that statement repeated, and repeatedly emphasized 
with examples, we can not have any conception of the 
prolific power of all life. For even observant people 
have very little opportunity to realize the abounding 
vitality of all animate nature. And most of us are 
not observant. JI, for example, hardly see one rat 
a year, hardly know an English sparrow by sight, am 
much impressed by the way my trees and shrubs tend 
to die. I always see, year after year, the same num- 
bers of crows or buzzards or woodchucks. What do 
I know about the power of life to multiply? 

And yet even my dull eyes have seen a few cases 
of the swarming of animals. I have seen the sky 
darkened at midday by the grasshoppers that were 
preparing to descend on Nebraska corn-fields. They 
came, as they come in Africa, from some distant 
breeding-grounds in hordes so vast and destructive 
and swift that they stagger the imagination. About 
the middle of the last century a sudden pest of cat- 
erpillars appeared in the forests of Prussia; so nu- 
merous were they that the noise of their droppings 
was like the rustle of rain. 

Most Americans have seen potato-beetles, and 
some have speculated on their numbers. The history 
of these humble beetles is more extraordinary than 
the tale of Tartar tribes. For unnumbered centuries 
they had lived a hard obscure life in Colorado, feed- 
ing meagerly on a plant that belongs to the genus of 
tobacco and potato. About 1850 one of them sniffed 


82 EVOLUTION FOR JOHN DOE 


something delicious in the breeze. She flew in that 
direction and lighted on a cultivated potato plant that 
was in a new settler’s garden. The power of fertil- 
ity increased with this new food supply, and across 
the fields of the juicy helpless leaves it took its dev- 
astating course. Within a few years the potato-beetles 
became an advancing army; they spread north and 
south, deploying on the plains with a front one thou- 
sand five hundred miles wide and rolling eastward at 
an average speed of two miles a day during the two 
months of summer when they could breed. At the 
close of the Civil War the army had progressed across 
Illinois; in 1872 it was in eastern Pennsylvania; and 
three years later was reported in Vermont. If there 
had been food, and no enemy to spray with poisons, 
these beetles would by this time have been numerous 
enough to pave the earth with a layer of their wing- 
covers. 

There is nothing exceptional about such increase 
of numbers. It is an entirely normal case, one that 
would be duplicated in a few decades or centuries by 
any ordinary animal that found favoring conditions. 
It has been surpassed by the more recent increase of 
the cotton-boll weevil. Where this came from is dis- 
puted, but in 1894 it ‘‘appeared’’ in Texas, and ten 
years later the head of our Entomological Bureau 
declared: ‘‘The Mexican Cotton-Boll Weevil has the 
unique record of developing in less than twenty years 
from a most obscure species to undoubtedly one of 
the most important economically in the world.’’ He 
estimates that during the five years after 1917 it de- 
stroyed upward of a billion and a half dollars’ worth 
of property. He has not set any staff of clerks to 
figuring on the rate of multiplication of the little 
beetle. He has been too busy trying to fight down the 
increase of another boll weevil in Texas, a pink one 


THE STRUGGLE FOR EXISTENCE 83 


from India, that had the best of a four-year battle 
with the forces of the Bureau and multiplied enor- 
mously against all odds. In June, 1922, the press re- 
ports told us: ‘‘State commissioners of agriculture 
estimate that the boll weevils are about five times as 
numerous as they have been before at this period of 
the season.’’ 

Kivery book on evolution gives illustrations of the 
way each species is fitted to multiply boundlessly. 
One of them* says: ‘‘If every egg of the herring 
should develop to an adult fish, 1t would not be long 
before the Atlantic Ocean would fail to contain them.”’ 
Anothert cites the case of a species of white ants: 
‘A female, after it is full-grown, does nothing but lie 
in a cell and lay eggs, producing eighty thousand eggs 
a day steadily for several months.’’ <A third} con- 
tributes estimates of this sort: ‘‘A single fern-leaf 
of a common species produces about fourteen million 
spores; a tape-worm produces hardly less than one 
hundred million eggs.”’ 

It will be safe to repeat the statement that these 
cases are not exceptional; they represent the normal 
provision of many plants and animals for propagat- 
ing themselves. They are so commonplace that every 
author may set forth fresh ones. We must not length- 
en out our list unduly, but should indicate briefly the 
inconceivable fecundity of several other classes of 
life to whose existence we seldom give a thought. 
When I try to find earth-worms for bait, I seem to 
prove that they are a very restricted genus; but it has 
been shown that in rich soil there is an average of 
fifty thousand of them to the acre. There they work, 
unknown to me, patiently grinding up stomachfuls of 


*W. B. Scott, The Theory of Evolution. 
tJordan and Kellogg, Evolution and Animal Life. 
tWeismann, The Evolution Theory. 


84. EVOLUTION FOR JOHN DOH 


leaves and dirt for a little nourishment, and then cast- 
ing out the residue. ‘‘In many parts of England,”’ 
Darwin tells us, ‘‘a weight of more than ten tons of 
dry earth annually passes through their bodies, and 
is brought to the surface in their castings, on each 
acre of land.’’? Huxley reminds us that in the body of 
a living fly there may be ‘‘countless millions’’ of in- 
dividual fungus plants. When passengers on an ocean 
steamer see night after night the phosphorescence of 
the water, every sparklet of light in the steamer’s 
wake for the thousands of miles is made by an indi- 
vidual animalcule. In all parts of the tropical oceans 
are little coral animals that fasten themselves to 
rocks, like sea-anemones, and there make for them- 
selves a limy skeleton which remains after their 
death; so tremendous is their power of reproduction 
that they have built the Great Barrier Reef of Aus- 
tralia, one thousand two hundred miles long and in 
many places one thousand eight hundred feet thick. 
In stagnant warm water we find animalcules whose 
grotesque forms can be seen readily under a srnall 
magnifying-glass. One species has been found to 
breed at the rate of six hundred generations a year. 
It has been estimated that if every individual should 
breed in normal numbers for five years and if none 
died, the volume of the three thousand generations 
would be ‘‘approximately equal to 10’ times the 
volume of the earth.’’* Remind yourself that 101° 
means ten with nine hundred ninety-nine ciphers after 
it, and that such a sphere would include more space 
than astronomers have measured. 

It is easy enough to see why the animalcule does 
not continue its rate of increase—there is not space 
for it in the universe. It is clear why no fish has 
packed the ocean full and why elephants are not 


*L. L. Woodruff’s Foundations of Biology, page 375. 


THE STRUGGLE FOR EXISTENCE 85 


standing five hundred thick on every acre of land. 
The reproduction of every species—even if it were 
the only one in the world—is limited by the supply of 
food. And since there are half a million species of 
animals, each of which would like to fill the earth and 
would be quite able to do so, there must be a severe 
pressure upon every species by all the other species 
that are tending to swell in numbers and to occupy 
the same territory. Such a pressure must cause in- 
tense rivalry; it must restrict, must strongly check, 
the increase of each individual. This check upon the 
increase of numbers causes the ‘‘Struggle for Hx- 
istence.”’ 

As soon as we hear that ominous phrase, we nat- 
urally begin to think of warfare, of bloody design. 
Indeed the literature of evolution is dotted with hints 
of this sort, and of late years the story-writers have 
given us many pictures of the world of nature as a 
battle-ground where all feet are swift to shed blood, 
a cruel place where venom and claw make way with 
enemies, where ‘‘nature is red of tooth and fang,’’ 
where life is a ‘‘gruesome cockpit.’’ This horrible 
notion* is so generally held that it has been used to 
justify human warfare. The German Bernhardi ac- 
tually argued as crudely as this: ‘‘Wherever we look 
in nature, we find that war is a fundamental law of 
evolution. This great verity, which has been recog- 
nized in past ages, has been convincingly demon- 
strated in modern times by Charles Darwin.”’ 


*William J. Long in his Mother Nature has done good service by 
denouncing this notion as ‘‘an appalling and degrading superstition’’ 
(though his own notion is not one that many naturalists endorse). The 
ideas of ‘‘eruelty’’ and ‘‘terror’’ are not to be found in Darwin. 
Long’s book is only an amplifying of the description that Darwin 
gives as a summary at the close of Chapter ITI of the Origin of 
Species: ‘*When we reflect on this struggle, we may console our- 
selves with the full belief that the war of nature is not incessant, that 
no fear is felt, that death is generally prompt, and that the vigorous, 
the healthy, and the happy survive and multiply.’’ 


86 EVOLUTION FOR JOHN DOE 


In the main all such ideas are false. To compare 
the struggle of nature with human warfare is absurd. 
Because we human beings are cruel to one another, 
because we plunge into ruthless wholesale killing, be- 
cause we have tortured and enslaved and exterminated 
one another in our struggles for domination, we can 
not assume that the struggle for existence is similar. 
Only a gorilla has a right to such an argument. Be- 
fore any one can have a true view of evolution, he 
must thoroughly purge his mind of this common and 
deep-seated error. Before we go on in this chapter 
to picture the struggle for existence as it 1s, we must 
take time to see what is not. 

It is not what our sentimental human minds 
would suppose. If we conceive it as cruel, as fierce- 
minded, as warlike, we are making the old mistake of 
having the great sun of nature revolve around our 
little mental sphere. Nature is not bitter with human 
hate. Nor, on the other hand, is nature sweet with 
human sentimentality. Nature is as different from a 
man as the starry heavens are from their reflection 
ina pool. ‘‘Nature’’ is simply a name for The Way 
Things Are. In this great scheme of things we can 
not detect any plotting of altruism nor any exercise 
of cruelty, neither sympathy nor jealousy. To our 
poor senses nature may seem like a loving mother, or 
like a stern inexorable stepmother; but the beauty 
and the harshness alike are flimsy imaginings; they 
are not nature. 

The struggle for existence does not invite men to 
go to war nor certify that might makes right nor dis- 
courage charity. It is not hideous, but partakes of 
the beauty of all truth. It contains no cruelty, unless 
all facts are cruel. 

In the whole long history of false reasoning there 
is no funnier chapter than the record of how man has 


‘PULY JSaloAVS dl} 
Jo st uo yeduos oy} YySsnoy, ‘sty? ynoqe ,,71dya00 oulOsanis,, B JO YonU JON ‘ast] FO APISLOATP 
ay} MOYS 0} peyluseM ‘e10Yysves dy} JO Yool B UO SNIPeL Yout-euo0 BV UL QoUaJSIXO IOF O[GONAS OL, 





"99 O0Rg MOTJONIYSop 0} WIY WYono1q uoezydepe sty ‘pasuvyo suOTIIpP 
ueayM ynq {mel soddn sty ut suodvam oy} Fo onqata Aq sjsvoq oY} JO SULY SVM LOSI} YJOO}-1OqQeSs ay} FQNOp ON 





THE STRUGGLE FOR EXISTENCE 87 


sentimentalized the struggle for existence. He has 
shuddered at the fierceness of the tiger while digest- 
ing the beefsteak of a slaughtered cow. He has writ- 
ten poetry about ‘‘the pious robin’’; yet for every 
kill of a tiger a robin will slay his hundreds. The 
only relentless and unreasonable slaughterer on earth 
is man. No wonder that man, who exterminates moose 
and bison while he tolerates the marriage of idiots, 
is quite unable to comprehend the wisdom and purity 
of the struggle for existence that is decreed by nature. 

The struggle for existence is a contest in which 
there is no motive of cruelty, no lust for power over 
others, no desire to do harm to another creature. It 
is an effort by every creature to do his best, his ut- 
most, to live and have young. [Every force of his 
being is animated by these two elemental instincts: 
(1) he must live according to the law that nature has 
planted in him, and (2) he must obey the primal 
commandment to be fruitful. Every act in the natural 
struggle for existence is entirely innocent and whole- 
some. 

In another way the struggle is unlike what we 
might assume. It is not a universal combat in which 
every creature’s weapons are turned against other 
creatures. In a great variety of ways animals and 
plants are useful to each other, confer benefits on 
others in the course of seeking their own welfare—as 
when birds remove caterpillars from leaves. Success 
in the struggle often comes from avoiding competi- 
tion—as when the sage-brush grows on the desert 
where other plants can not live. 

In another and more important way the struggle 
differs from what we have so far dwelt on. It is to 
a large extent not a set of duels between individuals; 
the contest is often impersonal, unfelt, unsuspected. 
Perhaps an illustration from human life will be useful 


88 BHVOLUTION FOR JOHN DOE 


here: if an actor or an author pleases the public, his 
work may be highly paid for, and the income of some 
other actors or authors be reduced. Stevenson says 
that a successful author—who may be a shrinking, 
affectionate person—stabs other authors with his pen 
as surely as if he used a dagger. So impersonal and 
unsuspected may the struggle for existence be at 
times in human affairs. Much more is it true that 
the unreasoning lives of a large part of the animal 
kingdom may be passed without any consciousness of 
rivalry, in peaceful success. Success need not depend 
on the ability to kill. All through the millions of years 
of the geologic ages the armored fighters have per- 
ished; to-day one of the most prolific animals is the 
least offensive—the rabbit. The rats and beetles have 
not conquered in the strife by slaughter. Some of the 
most successful animals are those that organize a so- 
ciety, like the ants and bees, in whose colonies there 
is no individualism, but only a ceaseless, unstinted la- 
bor for the whole group. 

But the struggle, for all kinds alike, is none the 
less fierce and unremitting because it is indirect and 
unknown. It is pitiless. If a communistic society of 
bees can not find nectar in competition with other 
societies, it will fail to leave offspring as surely as 
the lonely pair of eagles that fail to strike enough 
victims in their wide domain of sixty square miles. 
When any kind of organism can not produce enough 
seed, or suck enough water from the ground, or resist 
a plague of fungus, or withstand a change of climate, 
it dies. There is no more tragedy about this for the 
individual than there is about the most successful life, 
for every individual, weak or strong, must die. The 
only difference is that, in the long run, the weak leave 
few offspring; the earth is peopled by those who leave 
most offspring. ‘‘Reproduce or perish’’ is the eter- 





THE STRUGGLE FOR EXISTENCE 89 


nal necessity. In this struggle to propagate, the mush- 
room feeds upon decaying matter, the condor wheels 
its lonely flight above the mountains, the fish feels 
its sightless way in caves and ocean depths, the mos- 
quito swarms beyond the arctic cirele, the snow-plant 
spreads its abundant red upon the ice-fields of cold 
heights, the beaver builds his dam. High and low, 
everywhere under the whole heaven, in every cranny 
of space, with every imaginable adaptation, the urge 
of life compels every individual to seek out a living 
and have young. 

Though we can learn very little about the adjust- 
ments in nature, we can guess at them to some extent 
by what we see when man disturbs any balance. As 
soon as the dry valleys of California were set to or- 
chards about fifty years ago, the cottony cushion scale 
multiplied upon them at such a rate that destruction 
was in sight. The orchards were rescued* by study- 
ing nature’s adjustments in Australia, the home of 
the scale. It was found that there the scale was kept 
in bounds by ladybird beetles; some of these were 
imported, bred and turned into the orchards; they 
promptly and completely played their expected part 
in the struggle for orchards. The cantaloupes were 
saved from a pest by a similar army of ladybirds 
brought by the bushel from the high Sierras. Man’s 
best, and often the only, way of coping with the mul- 
titudes of nature is to employ the troops of nature, 
as in fighting the gipsy moth, the Hessian fly and 
the grain aphis. We are in a perpetual contest with 
the hordes of life that swarm against our interests. 

Some such gross examples are about all that man 
ean learn of the interplay of forces that work in the 
struggle for existence. If we look at any landscape, 


*Mustering Nature’s Mercenaries, by Elizabeth A, Ward, iw the 
Forum tor Octcher, 1915, 


90 EVOLUTION FOR JOHN DOE 


we see that all forms of life are fitted into a mosaic 
where each can thrive to a certain extent, thus far and 
no farther. Hach is, in the ordinary course of the 
seasons, checked from dominating over others. Grass 
and spruce trees and violets and robins exist in 
abundance, and now one and now another may fluc- 
tuate somewhat in its numbers; but as the decades 
pass, the balance only swings to and fro about a cen- 
ter. Hach plant and animal is severely restrained by 
the whole competition. Year after year we look upon 
the same peaceful assemblage, hear the same songs, 
see the same bright blossoms, exclaim with the same 
satisfaction at the restful peace of it all. 

But there is no peace. In any landscape each leaf 
and beak and fin is tirelessly at work to keep up its 
numbers. Every plant bears seeds in prodigious quan- 
tity; every animal’s body is a factory of countless 
eggs or sperms. With all the power of every mother’s 
being there is effort to rear young. Every pair of 
individuals is doing its best to leave descendants that 
would spread over the whole region. With what re- 
sult? Only this: that next year, and ten years hence, 
and fifty, and a hundred, there will probably be the 
same number of descendants. All this ceaseless power 
is somehow held in check by the competition of pow- 
ers. Of all the seeds that are formed by a plant with 
such lavish extravagance only a few sprout. ‘‘There 
is a British starfish which produces at least two hun- 
dred millions of eggs, and yet it 1s not what one would 
call a common animal.’’* There is something fear- 
some about such tremendous possibilities that accom- 
plish no more than just to keep the numbers of this 
starfish from decreasing. Many of the lower ani- 
mals hatch a thousand eggs to insure one offspring. 
And only a small fraction of the young can grow up. 


*J. A. Thomson, The System of Animate Nature. 


THE STRUGGLE FOR EXISTENCE 91 


The rearing of all the offspring with such intense 
devotion has only one result, that when the years have 
passed and the parents have died, there are two other 
members of the species to take their places. 

Here is a fact to which the ordinary citizen never 
gives a thought. The pretty scene that he surveys 
from a porch or a canoe is a cemetery for the young 
that never mature. We need not weep their fate, but 
we observe the fact. This is the struggle for existence. 


CHAPTER VII 
VARIATION 


THE previous chapters have been descriptions of 
life as a naturalist sees it—bird’s-eye views of what 
plants and animals are like. In this chapter and the 
next two we shall spend some of the time studying the 
inside of eggs.* Ata point where the course changes 
in this way we had best look back a minute to see what 
ground we have covered. 

The first four chapters, displaying the myriad 
forms and the tangled web of life, were a preparation 
for Adaptations. Until we realize something of the 
intricacies of life, we can not see much of a mystery 
about their adjustments. When we have had a good 
look at Adaptations and have wondered how they were 
made, we are ready for the explanation. The explana- 
tion is in four steps: The Struggle for Existence, 
Variation, Heredity, Natural Selection. The first of 
these (in Chapter VI) was a view of the way every 
form of life is doing its best to multiply, though it can 
seldom do more than hold its numbers even. Looking 
at this struggle was a survey of the facts as a natural- 
ist sees them. 

*A biologist uses ‘‘egg’’ to mean the female germ of either 
au animal or a plant. After the fertilized egg of a plant has reached 
a certain stage of its development as an embryo, the development 
ceases; and this dormant embryo is what we know as a seed. It 
would be convenient, and perhaps not misleading, to speak of eggs 
and seeds as synonymous terms in this elementary book, but a biologist 


could not tolerate such a use of words. ‘‘Egg’’ in this chapter 
means auy fertilized germ-cell of any plant or animal, 


o 


VARIATION 93 


But Variation is different. Here we quit tramping 
in the open with Darwin and Wallace; we are in the 
laboratory, looking through the microscope at revela- 
tions that have been made since Darwin died. 

Variation,* as used in this chapter, means simply 
the fact that young are never precisely like their 
parents. We know that no child ever exactly resem- 
bled its father and that no tree was ever an accurate 
reproduction of its mother. We do not need to be 
told that among all the races of men in all time there 
were never two exact duplicates, and we can believe 
that no two flowers are ever so similar that a micro- 
scope would not show differences between them. We 
are as familiar with variations as we are with a clover 
leaf; but we have never been inside of them, never 
have realized what it means in nature’s architecture 
to vary a pattern. 

The extremes of such variation are called monstros- 
ities. The Siamese Twins were two men joined to 
each other by a thick tube of cartilage, through which 
their vital organs were so closely connected that no 
surgeon dared cut them apart. They were very 
unlike their parents. The Bohemian T'winst were a 
pair of women who had only one spine between them. 
When they died, the courts had to decide whether the 
twins were one person or two persons. This two-in- 
one body bore no resemblance to its parents or ances- 
tors. Peppino Magro, twenty-two inches tall when 
fully grown, and Kazanloff, one hundred and eleven 
inches tall, varied from their parents in stature. They 
were born with some peculiarity of a little gland which 


*Note for any critical reader: This chapter has little to say 
about the distinction between somatic modifications, recombinations 
of genes, and germinal mutations. These technical questions are 
gutlined in Chapters XXII, XXIII and XXIV (Section III), 


tThe Blazek sisters, who died in Chicago, Mareh, 1922, 


94: EVOLUTION FOR JOHN DOE 


directed their growth abnormally. A baby that is 
born without arms, or with a jaw-bone growing in its 
body, or with a full set of teeth, or with a hairy nose 
and forehead, or with a tail, shows a decided variation 
from normal parents. 

Animal monsters are constantly being exhiiitnd 
and reported: Siamese twins among fishes have been 
the special study of one French zoologist. Calves are 
born with an extra pair of little legs hanging from the 
shoulder, or they have peculiar heads and are called 
‘‘dog-headed’’ or ‘‘human-headed.’’ A. cat has been 
born with only two legs, on which she learned to walk; 
and a lamb has lived without any legs. A stag may 
have one of its antlers growing downward. 

Among plants there is no end to the monstrosities 
that are frequently seen. Ears of corn are double or 
distorted, or have unnaturally arranged kernels. A 
little peach sprouts from the cleft of a large one, or 
a kind of second orange may appear at the base of an 
orange. A bean, which normally sprouts with very 
large leaves, at the base of which are little insignifi- 
cant scales, may show gigantic scales and no leaves. 
If we ask what caused these peculiar variations, we 
ean think of only one answer: something abnormal 
occurred in the development of the egg. What does 
that mean? What are we talking about when we ecare- 
lessly pronounce the words ‘‘change in an ege’’? If I 
may judge others by myself, we are thinking of noth- 
ing at all. People spend intellectual lives, studying 
psychology or art or history, with no more curiosity 
about an egg than if it were a drop of water that may 
change into steam or ice according to the temperature. 
Yet a germ-cell is a compound of unexampled marvels, 
more intricate than the whole galaxy of suns and 
nebulas, containing in its deep recesses secrets which 
lie far beyond the reach of the most skilful user of a 


VARIATION 95 


microscope. A germ-cell is life. We shall never know 
much about it until we have penetrated all the rest 
of the universe. 

But something has been learned—enough to show 
in a general way the course of the evolution of life upon 
the earth. It is very recent knowledge, hardly 
seventy-five years old. Within those years all the 
understanding of the nature of plants and animals has 
been revised by learning about ‘‘cells.’’ Thirty 
years ago the study of these was largely devoted to 
the masses of them in tissues (called ‘‘histology’’) ; 
nowadays the college courses attack the cell directly; 
everything is cells, cells, cells. An old-fashioned 
person may grow weary of this chorus that perpetually 
wells from all our laboratories; but as soon as he dis- 
covers the reason for it he must sympathize. The 
study of the cell has given us the greatest revelation 
of how nature works in molding life. 

Recall that time when we stood within a clover leaf 
gazing through the crystalline walls of a cell, behind 
which surged the streams of protoplasm. We watched 
the varying gray mass of viscous liquid, within which 
we could faintly see strands of fiber forming some 
sort of open mesh. It was a piece of life, complicated 
and specialized for its own duties. Its core was water 
and sap; around its walls, in the protoplasm, were the 
ereen sugar-making globes; the protoplasm flowed 
from point to point, directing all the details of a sugar 
factory. It could repair its own walls, summon water 
and gas, send out oxygen, ship its products out 
through connecting veinlets. It had a skill that lies 
beyond understanding. In other cells this protoplasm 
knew how to transform food and energy; in others it 
made the roofing material; in others it concocted oils 
or fats or colors. It transmitted orders to the workers 
in the pores and hairs and veins. Hence it is more than 


96 EVOLUTION FOR JOHN DOK 


a substance that a chemist can analyze; it is beyond 
analysis. It is not a certain kind of, material, any 
more than jelly-fish and lions could be called the same 
kind of animal material. ‘‘Protoplasm’’ is only a 
convenient name for our blindness when we look into 
cells. Since we can not detect the differences, we give 
the name ‘‘protoplasm”’ to the living matter that we 
see. 
If we had observed the protoplasm of the clover- 
leaf cell as clearly as the highest-power microscope 
does, and had had a guide to tell us where to look, we 
could have distinguished in it a little body, no larger 
than one of the sugar-making globes, the ‘‘nucleus.’’ 
In this small globule is contained the guiding power 
of the whole cell, as if it were the office of a factory. 
It is this nucleus which directs the birth of a new cell. 

Are you at all startled by hearing about ‘‘the 
birth’’? This cell that we are looking at—this subtle 
aggregate of powers—could no more happen into 
existence than a camel or a whale could, for it is an 
organized unit of life. If I see a hawk flying over- 
head, I know that he was once an egg and was born. 
It is just as obvious that the cell was born. It must 
have grown out of a cell, which had grown out of a. 
previous cell, which had grown from a previous cell. 
There can not have been any gap in the series of de- 
scents from the time when life began on the earth. 
Every cell, in every leaf and muscle and brain, is the 
offspring of some previous cell. 

The origin of a cell in a clover leaf can not be any 
hit-or-miss process; a new cell can not ‘‘just branch 
off somehow.’’ Even a beet-sugar factory that man 
makes—a clumsy pile of apparatus for doing the sim- 
plest sort of crude work—has to be designed by an ar- 
chitect with elaborate fulness. There must be complete 
blue-paper plans, an engineer’s care to have founda- 


VARIATION of 


tions solid, a builder’s minute pains to have walls kept 
plumb and courses of brick level, expert work to make 
steel girders exact, expert manufacture of vats and 
engines, high technical skill to furnish spectroscopes 
and chemical reagents. If so lumbering an institution 
as a man-made factory requires all this provision, 
much more will the creating of so intricate an organ- 
ism as a plant cell. Of all the secret processes in a 
cell not the least jot of a small item of one can be left 
unprovided for. 

The specifications for a future cell lie in the 
nucleus. When this receives the impulse to reproduce, 
its mechanism is set to work, and it operates its hun- 
dreds of minute parts with an accuracy that is awe- 
some to think of. So small is the space within the 
nucleus and so dim are the outlines of operations that 
no scientist could ever have charted the scene by him- 
self. But after a generation of work the experts are 
now able to give us some picture of the steps of a 
birth. 

They tell us that in the course of half an hour or 
more the following program is carried out: First the 
nucleus spreads out to occupy a larger portion of the 
cell. Several loops appear in the liquid; they grow 
shorter and thicker and become straight; they then 
arrange themselves in the center of the cell, as if they 
were so many bits of a small thread, placed end to 
end in a plane. Each of them splits down its length 
into two equal parts, as if a fine knife had been driven 
through the bits of thread and had divided them 
all at one blow. Thus the original tangle of 
loops has been separated in an orderly manner into 
two equal sets of straight pieces. The two sets now 
draw apart, moving away from the equator of the cell 
toward opposite poles. Meanwhile the whole cell has 
been preparing to divide: a groove has appeared on 


98 EVOLUTION FOR JOHN DOE 


its outside, as if made by a string that had been drawn 
tight around it in the same plane where the little 
bodies split within the nucleus. The groove grows 
deeper and deeper, till the cell is split in two. The 
result is two small cells, each composed of half of every 
detail of the previous cell, each with a complete equip- 
ment of cell life. These grow quickly to full size and 
are now prepared to reproduce in the same way as 
often as they have orders to do so. 

That brief sketch of cell birth may give a wrong 
impression by its comparison with ‘‘bits of a thread.”’ 
Of course the real processes, if our senses were fine 
enough to see them, would appear as a set of countless 
adjustments made rapidly with supreme nicety. And 
perhaps the erude sketch has made a reader forget 
the size of the space that encloses all the operations. 
The whole cell is so small that it may not take up 
more than a millionth part of one leaf. Of the minute 
space in this cell the nucleus fills only a fraction. 
Even within the nucleus all the complexities of a 
future organism are arranged for in one small part of 
the space—that is, in the bodies that split apart. The 
mind can not begin to comprehend such close packing 
of forces; it quits exclaiming about ‘‘marvels’’ or 
‘‘unspeakable mysteries’’ because any words of won- 
der fall so far short of what we feel. 

The best we can do is to accept the bare fact that 
in those infinitesimal loops at the limit of microscopic 
vision is packed the complete outfitting for the whole 
life of a daughter cell. These are called ‘‘chromo- 
somes,’’ a word that means ‘‘color bodies.’’* Every 
one of the cells that make up flesh or wood 
or animalcules arose in this way by means of chromo- 
somes. They can create a new cell that inherits all 


*So named because they were first made visible by coloring them 
with a stain. 


VARIATION a9 


the peculiarities of the old one, and hence they are 
called ‘‘the carriers of heredity.’’ 

There are endless varieties of cells. The live bark 
of a tree is built of several kinds, each with its own 
individual sort of protoplasm to keep up its activities. 
Bone and mahogany are made by protoplasm that 
builds hard walls for its cells, and then dies. In the 
brain are cells where protoplasm keeps records of 
sensations and manages switchboards for sending 
messages to other cells. A nerve-cell is a long, slen- 
der fiber. In a cubic inch of normal human blood 
there may be seventy billion cells, fitted to do special 
chemical work or to rush as soldiers against invading 
forces. The small red ones are generated in endless 
billions by mother cells that live in the bones. There 
are cells that lead separate lives as individual animals 
—like an ameba, for example, which is a single cell 
that opens up any part of itself for food. 

Cells are of all sorts, of all degrees of complexity ; 
but all alike originate by the mechanism of chromo- 
somes. 

Before we go on to describe the variations that 
originate in chromosomes, it may be well to speak of 
a common misconception, one which used to mystify 
me. I refer to the use in older books of the word 
‘‘simple’’ to apply to germ-cells. ‘‘Simple’’ means 
only that the cell is ‘‘single,’’ that there is only one of 
it. The human eye is called ‘‘simple’’ in comparison 
with the multiple eye of a fly. In this sense we might 
say that Paris is a ‘‘simple’’ city and George Wash- 
ington a ‘‘simple’’ man—because the city and the 
general are not compound. A ‘‘simple’’ cell may be, 
potentially, as intricate as an animal. 

Keep that statement in mind when you hear that 
every egg is a cell. A grain of clover pollen is a cell. 
Inside of this is a nucleus, within which are the chro- 


100 EVOLUTION FOR JOHN DOE 


mosomes. They are what count.* They carry all the 
specifications for a whole new plant, for all the types 
of cells that are to form roots and ducts and stems and 
leaves and hairs and blossoms and future seeds. In 
them are, potentially, all the structures of the next 
eeneration, complete to every least item, such as mak- 
ine each hair taper to an end that is somewhat 
pointed, but rather blunt and irregular. The chromo- 
somes are faithful agents, powerless to disobey, for 
carrying out these specifications. They can not con- 
struct grass or huckleberries; they can not construct 
another kind of clover; they can only reproduce a 
plant like the one from which they came. 

This holds true for every egg of any kind of plant 
or animal. In every egg there are some chromosomes 
within a nucleus, and their development is all deter- 
mined in advance: they are compelled to build their 
new life on the pattern of the parents. No earthly 
power can reach inside the chromosomes and make a 
new pattern for them to follow. Nor is there any way 
of so altering a parent that its reproducing cells will 
create a different species of body. However much you 
may mutilate a clover plant or a fowl, if you allow the 
ege-making organs to work at all, they will produce 
the only type of egg that they are fitted to produce. 
They must make the identical kind of chromosomes 
that their parents made and that their offspring will 
make. The business of chromosomes is to reproduce 
by the given pattern. 

Yet, in spite of this, their machinery is never pre- 
cisely perfect. Jt does sometimes vary the pattern, 
That is variation. : 

We know next to nothing about the reasons why 

*A cytologist would find this statement over-simplified, for there 


is no doubt that the other contents of the cell have their part in repro- 
duction. See E. B. Wilson’s The Cel, (1925) Chapter IX. 


VARIATION 101 


chromosomes vary from their normal operations, but 
ean only notice that they do vary. Their inexactness 
is not surprising. Indeed the wonder is that in such 
intricate work as theirs they ever can follow the model 
as closely as they do. We should naturally expect 
that there would sometimes be slips or failures in the 
machinery. 

Variations are sometimes spectacular, giving rise 
to a new variety or species. In 1791, on a Massachu- 
setts farm, was born a ram whose legs were so short 
and body so long that he was nicknamed the ‘‘otter’’; 
he was valuable because he could not jump fences, and 
he became the founder of a new breed of sheep called 
the ‘‘ancon.’’ Forty years later the same sort of 
thing happened on a farm in France. A ram was born 
with a large head, long neck and legs, covered with 
smooth silky wool; he was the forefather of a new and 
valuable kind of sheep. Such sudden creations, or 
‘‘sports,’’ are decided alterations that chromosomes 
make in the pattern they are supposed to follow— 
‘“‘happy mistakes’’ we might call them. Such a mis- 
take certainly brought joy to a Kansas farmer in 1889, 
who one day found that a young calf in his herd of 
Hereford cattle had no horns; it founded the race of 
‘‘nolled Herefords.’’ 

These great variations are celebrated because they 
were so useful to man and were as romantic as the 
discovery of a new diamond mine. Yet they show no 
more peculiar shifts in chromosomes than many cases 
that are only curious freaks of passing interest. Man 
has never taken advantage of the forgetfulness of a 
chromosome that did not put a tail on a colt. 

There was once a set of chromosomes in an orange 
that did not put in any seed-making apparatus, and 
that ornamented the base of their work with a queer 
whirl. An orange-grower noticed this sport and liked 


102 EVOLUTION FOR JOHN DOE 


it; since then the ‘‘navel’’ orange has been on all our 
fruit-stands. A dozen years ago Professor Cockerell* 
saw in Colorado a native sunflower, a wild plant, that 
was red. Here was something new in the world, a 
sport produced by a chromosome that had transferred 
the coloring matter from the disk, where it belonged, 
to the flowers at the edge of the disk. So rarely is 
such a slip made that, with one possible exception, no 
other case was ever reported. Darwin exclaims thus 
about a sporting plum: ‘‘When we reflect on the mil- 
lions of buds which many trees have produced before 
some one bud has varied, we are lost in wonder as to 
what the precise cause of each variation can be.’’ To- 
day we may still be ‘‘lost in wonder’’ if we try to 
imagine just the motions that a chromosome would 
make in building a new variety of plum, for the mo- 
tions and materials are beyond our range of imagina- 
tion; but we can now understand in a general way that 
in the mechanism of chromosomes there may once in a 
while be a shift of gears and that such alterations may 
be fortunate. 

One of the most useful plants for man is wheat. 
Its chromosomes are restless and variant; one French- 
man claimed that he had cultivated over three hun- 
dred varieties. Though most of these sports show 
only slight differences, occasionally there is a large 
and decided one. About twenty years ago in Canada 
two different varieties were mated; the chromosomes 
were so stimulated to mix up and recombine their ele- 
ments that a hundred variations resulted, one of 
which—it appeared on only a single stalk—proved to 
be a hardier plant with better bread-making qualities 
than North America had known before. It was named 
‘‘Marquis.’’ A century ago this fact of the sudden 
sporting of wheat was known; a famous Scotch grow- 


*T. D. A. Cockerell, Zoology. 


‘sqyueid pues syeutue [[e@ Jo yaed A19A0 Ut 
se ‘Apoq ay} Fo 4avd sty} ut uorqerrea pengodiod st a1oyy saytTe A[JOVXO O1OM ZVI SLo[JUL PLY LoAO SNO {tvs OA) ON 





‘poof FO spury 
Aueut ttoy} Aq popvorput st skvM OSIOATP Jsow oY} UT poAdzoao oavy AoY} MOF “PLLOM oY} ttt osfo otoyMAIoOAD (uINS 
-sodo oy} tof ydooxo) youryxo owvooq yey} sperdnscew oy poArosord sey oys oxoyA ‘wnosnuTt S,oInjVN Sl BIpeisny 





VARIATION 103 


er* testified that he had never seen grain which had 
been improved ‘‘by cultivation,’’ but only ‘‘by select- 
ing the new varieties which nature occasionally pro- 
duces, as if inviting the husbandman to stretch forth 
his hand and cultivate them.’’ In 1819 he ‘‘observed 
quite accidentally a single plant of a deeper green and 
more heavily headed out’’; this he cultivated, and it 
became one of the best kinds for the region where 
Walter Scott lived. 

In 1923 ‘‘a single branch of red apples was sold by 
Lewis Mood of Ferrell, New Jersey, to a nursery firm 
for five thousand dollars.’’ The year before ‘‘fifty 
thousand dollars was paid for a single strawberry 
plant by the R. M. Kellogg Company of Three Rivers, 
Michigan, to its grower, Harlow Rockhill, of Conrad, 
Iowa.’ ’t} , 

So far as we know, all improvements in domesti- 
eated plants and animals came about in sudden varia- 
tions, sometimes by a long leap and sometimes by a 
great number of very short steps; they appeared as 
unearned gifts from the chromosomes. We have rec- 
ords of a golden-colored grape that sprouted from a 
black variety in England, of ‘‘a multitude of varieties 
that sprang from one seed’’ in a French vineyard, and 
of new hothouse varieties that are produced ‘‘almost 
every year.’’ Hach kind of apple was originally a 
solitary sport, a unique product, made by changeful 
echromosomes.t No new kind of peach was ever at- 
tained by effort, but always by discovering a novelty 
hanging on a tree. If an agricultural experiment sta- 
tion should try for a century to train the seeds of a 


*Shirreff, of whom Darwin says, ‘‘A higher authority can not be 
given,’’ 

tAssociated Press ‘reports. 

fSuch changes may not be an appearance of a character that 
was never in the heredity; they may be only ‘‘reeombinations’’ of 
ancestral characters, in such a way that the new combinations can be 
inherited. See Chapter XXTV, Section ITI. 


104 EVOLUTION FOR JOHN DOE 


potato, it would fail; its only hope is to be on the look- 
out for what the seeds have happened to bring forth. 

Chromosomes tend to make some of their varia- 
tions repeatedly. Every one knows that most clover 
leaves grow in clusters of three, but that in any field 
there are several clusters of four and may be clusters 
of five or more. Men have always observed that some 
pigs are born with a solid hoof instead of the usual 
two toes; pigs may occasionally have a third toe, or 
a pair of bristly tassels under the throat. Most col- 
ored animals occasionally have white young, and 
these albinos are often less hardy than the parents, 
being less able to withstand heat or poisons or para- 
sites. In any flock of peacocks there may suddenly 
appear a bird of smaller size with black shoulders, as 
if the chromosomes of this animal were prone to make, 
every so often, this particular kind of variation. The 
shell of some species of snails regularly grows in the 
direction in which the hands of a clock move, but ocea- 
sionally specimens grow in the opposite direction. 
Human chromosomes give a small percentage of us 
two-jointed fingers or freakish powers of multiplying 
mentally. 

If only one double thumb or one four-leaf clover 
had ever been seen, we might suppose that chromo- 
somes had strange independent powers of their own, 
that they were like people who enjoy playing a joke or 
inventing a novelty. In the same way a South Sea 
Islander who had seen only one motor-boat in his life 
would suppose that the engine had mental powers of 
its own and was a kind of harnessed demon. But any 
civilized man—though he may speak of an engine as 
‘facting badly’? or may swear at the ‘‘perversity of 
inanimate objects’’—knows that an engine must fol- 
low the set laws of mechanics. Every biologist knows 
that chromosomes are absolutely bound by the fixed 


VARIATION 105 


laws of physiology; however ‘‘comical’’ or ‘‘bun- 
eling’’ their work appears, they are just as passive 
organs as a heart or a blossom is. 

And even when they produce a novelty their work 
is, more often than we think, of a routine sort, like 
putting color in the unusual place or putting on a 
fourth leaf. The celebrated Dutch botanist de Vries 
warns us that when we see in a bed of white flowers 
one blossom with a bluish tint this unexpected blos- 
som may not be a real sport. He knew how often the 
irregularities occur regularly. In his search for real 
sports he found a varying primrose that promised 
well; he observed its variations for sixteen years, and 
in 1903 published a big book on the subject. He believed 
that his primrose had sported into seven distinct new 
species and into many others that were less decided. 
He described ‘‘the very first moment of the appear- 
ance of two of the new stout species’’ and said that 
‘‘they seemed to have inherited the capacity of pro- 
ducing in their turn new mutants.’’ Mutant was his 
word for a new species that suddenly sprang into ex- 
istence; on this idea of ‘‘mutation’’ he built a theory 
that has been the talk of the learned world for twenty 
years. Yet those ‘‘new species’? whose birth he cele- 
brated have also sprung into existence on Long 
Island, and have also sprung into existence in Eng- 
land, and perhaps have been born regularly at inter- 
vals for centuries, like so many five-leaf clovers. 
Possibly de Vries fell into the same trap that he 
warned us amateurs against. Thus we see that varia- 
tion is an extremely complicated matter, about which 
there is still much to learn. : 

You and I seldom take notice of differences in na- 
ture between the parent and the young. Even the ex- 
perts sometimes fail to find them: the goose, though 
domesticated for thousands of years, has shown hard- 


106 EVOLUTION FOR JOHN DOE 


ly any changes. But almost always the close observer 
finds the variations, as this quotation illustrates: 
‘“‘Mr. Bates, after examining above a hundred of the 
big beetles, thought that he had at last discovered a 
species in which the horns did not vary; further re- 
search proved the contrary.’’ If a specialist can 
make such a wrong supposition, surely the rest of us 
need to see the universal truth displayed in a series 
of quotations from men who know by long study that 
chromosomes can never be trusted to be absolutely ex- 
act: ‘‘I have seen it gravely remarked that it was 
most fortunate that the strawberry began to vary just 
when gardeners began to attend to this plant; the 
truth no doubt is that it had always varied.’’ Of 
course it was the truth; three hundred years ago some 
shrewd gardener ‘‘availed himself of the inherent 
power of variation possessed by the plant.’’ All beans 
may look alike, even to the most sharp-eyed grower, 
but ‘‘after two severe frosts only three of the three 
hundred ninety scarlet-runners remained, not even the 
tips of their leaves being browned; it was impossi- 
ble to behold these three plants, with their blackened 
dead brethren all around, and not see at a glance that 
they differed widely in constitutional power of resist- 
ing frost.’’ ‘‘The gold-fish, from being reared in 
small vessels and from being carefully attended to by 
the Chinese, has yielded many races.’’ ‘‘Where flow- 
ers are grown by the acre for. seed, scarcely a season 
passes without some new kinds being raised.’’ Nat- 
uralists tell us just as emphatically that wild plants 
and animals show the same tendencies as the domestic. 
The wild orange plants in the jungles of India have 
the characters of the bitter variety, ‘‘but occasionally 
wild oranges occur with sweet fruit.’? ‘‘The chestnut 
trees may possibly survive the present blight, because 
there may be here and there one that contains a secre- 


VARIATION 107 


tion which will kill the attacking fungus; there are 
such trees in Asia, whence the blight came.’’ ‘‘Our 
common forest trees are very variable.’’ ‘‘It is prob- 
able that all insects occasionally show some abnor- 
mality of wing venation.’’ ‘‘The description of new 
mutant types in almost every plant and animal that 
has been carefully examined indicates the very gen- 
eral occurrence of definite mutations.’’ The prevail- 
ing fact of variation is put thus emphatically by 
Wallace: ‘‘We find no evidence of greater variations 
in domesticated animals than in wild ones.’’ 

Any one may become an investigator for himself 
if he is curious about variations in nature. Gather a 
dozen potato-beetles and scrutinize the brown stripes 
that mark their wing-covers. The first one that I saw 
this spring had between two of his stripes a heavy 
cross-bar that would have earned him a nickname if 
he had gone to school. ‘Though his scientific name 
(decemlineata) means ‘‘ten-lined,’’ he often fails to 
show ten lines on his back. The veins on the wings 
in any species of fly are usually so true to a pattern 
that they can be relied on as a mark for classifying; 
but careful examination of a few hundred wings will 
show that they are not precisely similar. 

Darwin, an exceptionally keen-eyed naturalist, 
often marveled at the skill with which breeders of 
animals detected slight variations that were invisible 
to him: ‘‘In the great majority of cases a new char- 
acter is at first faintly pronounced, and then the full 
difficulty of selection is experienced. . . . The fin- 
est powers of discrimination and a sound judgment 
must be exercised. . . . I have been astonished when 
celebrated breeders have shown me their animals, 
which have appeared all alike, and have assigned their 
reasons for matching this and that individual. . . . 
The best flock-masters do not trust to their own judg- 


108 EVOLUTION FOR JOHN DOH 


ment or that of their shepherds, but employ persons 
called ‘sheep-classifiers.? When the lambs are weaned, 
each in his turn is placed upon a table, that his wool 
and form may be minutely observed... . Those 
alone who have associated with pigeon fanciers can be 
thoroughly aware of their accurate powers of discrim- 
ination acquired by long practice. I have known a 
fancier deliberately study his birds day after day. 

. . Sir John Sebright used to spend two or three 
days in examining, consulting, and disputing with a 
friend which were the best of five or six birds... . 
Wherever silk is produced, the greatest care is be- 
stowed on selecting the cocoons from which the moths 
for breeding are to be reared. Near Shanghai the 
inhabitants of two small districts have the privilege of 
raising eggs for the whole surrounding country, and 
that they may give up their whole time to this busi- 
ness, they are interdicted by law from producing 
gilk,’? 

We know that only persons with inborn talent, 
trained by long experience, are fitted to judge at 
shows of dogs or poultry or cattle. These judges are 
experts In variation, and to them no two animals ever 
appear identical. Exact reproduction is never to be 
found. In the patterns made by chromosomes there 
is perpetual variation. 


CHAPTER VIII 
HEREDITY 


Every reader of this book knows that the sun does 
not move around the earth. Also he knows that the 
moon does move around the earth. These two heav- 
enly bodies, which appear to be of the same size and 
to move in the same way through the same path over 
our head, are as different in size as a grain of sand 
and a baseball, as different in motion as the second 
hand and the hour hand of a watch. The moon does 
what it seems to do; the sun is deceptive. 

There are two principles in evolution which seem 
like counterparts of each other—Variation and Hered- 
ity. Heredity is hke the moon—it is near to our 
common knowledge and it is what it seems to be. Vari- 
ation is the sun of the system—much larger than it 
appears, more remote from our understanding, and 
deceptive in its motion. All evolution revolves around 
Variation. All evolution is determined by the fact 
that chromosomes never reproduce exactly. As you 
read this chapter and the next one, keep your mind on 
Variation as the center of the whole theory. College 
teachers who have hammered away at this subject for 
twenty years testify that the minds of students are 
always forgetting that the prime cause is Variation. 
Many a college graduate, fresh from his course in 
biology, will falter and go wrong in trying to explain 
the subject because he forgets to start with Variation. 
That is the reason why Variation was described so 

109 


110 EVOLUTION FOR JOHN DOE 


emphatically in the previous chapter. It was put be- 
fore Heredity and Natural Selection. Fasten your 
mind to the variations made by chromosomes. A use- 
ful slogan among students is ‘‘keep your eye on the 
chromosomes.’’ 

It is small wonder that we all tend to put the ex- 
planation wrong-end-to.. The whole world always had 
it hind-side-foremost until 1859, and in every-day life 
we invert the truth as naturally as we say that ‘‘the 
sun rises.’ | 

Consider a pair of examples. The first is the color 
of the negro. I always used to suppose that Adam 
was a white man, that some of his white descendants 
migrated to Africa, that the first generation of them 
was tanned by the tropical sun, that their children 
therefore inherited a somewhat browner skin, and that 
the grandchildren were somewhat browner still, until 
finally the race became so thoroughly brown that it 
was black. I never asked myself, ‘‘How could sun- 
burn be inherited?’’ When a man has learned to keep 
his eye on chromosomes, he can see that no amount of 
tanning will alter the skin-making part of that mech- 
anism. The second example is bow legs. It is nat- 
ural to take it for granted that about a thousand 
years ago Spanish men became bowlegged from riding 
horse-back, and that in the course of thirty genera- 
tions of knights and vaqueros each child inherited the 
bow legs that his father had acquired by clasping a 
horse for twenty years. We never inquire how this 
exercise of leg muscles could enter the germ-cell, then 
penetrate the nucleus, and then set up alterations in 
the infinitely delicate and complicated mechanism. 
The notion is absurd to any one who will keep his eye 
on chromosomes. 

Less than a century ago the whole world assumed 
that acquired tan and muscle-development could be 


PEO LU Nar er) 111 


inherited. The most learned scientists believed that 
if a man enlarged his forearm by labor or trained his 
fingers to write a good hand, his son would in conse- 
quence have a bigger arm or write the same kind of 
hand, All the great naturalists of Kurope thought 
that if a giraffe continually stretched her neck for 
food, the offspring would inherit some of the strength 
and stretching ability that she gained by this exer- 
cise. 

This is a very common idea, on which we have all 
been brought up. We naturally take it for granted 
that if we train two generations of pointers the third 
generation of pups will inherit more ability to stand 
motionless, that if we keep the feathers plucked from 
ten generations of hens the eleventh brood of chicks 
will have scantier plumage. This common and natural 
idea used to be accepted as the theory that ‘‘acquired 
characteristics can be inherited.’’ A ‘‘characteristic”’ 
means any item of the bodily or mental make-up, such 
as white hair, big biceps, thick fingers, weak lungs, 
keen sense of smell. It is the word that Darwin used, 
and is the natural one, but nowadays the scientists 
use instead the shorter word character. ‘‘ Acquired’? 
means produced in the body during its lifetime. Thus 
if a parrot’s tongue is slit or if a lion learns to live 
on vegetables or if a blacksmith’s arm is increased in 
size by wielding a hammer, the changes thus made in 
their bodies are said to be ‘‘acquired characters.’’ 
The theory taught that if we cut off the tails of a 
male and a female cat, their offspring might, as a 
result of the amputations, be born without tails. Even 
so late as 1887 there were exhibited at a Naturalists’ 
Congress in Germany some kittens that were said to 
have been born with only stumps of tails because the 
mother had lost her tail by an accident—that is, she 
had ‘‘acquired the character of taillessness.’’ And 


112 EVOLUTION FOR JOHN DOE 


even the most famous promoter* of the cell theory 
took the exhibition seriously! Scientists gravely lis- 
tened to stories of how a dueling scar was inherited 
and how 4 man’s frozen thumb caused misshapen 
thumbs in his grandchildren. 

All through the nineteenth century the scholars 
discussed the question, ‘‘Can scars be inherited?’’ 
The greatest German philosopher argued before Dar- 
win was born that they could not be, and in Darwin’s 
old age the greatest English philosopher was still 
arguing that they could be. The debate might have 
gone on till doomsday if a common-sense biologist 
named Weismann had not cut off the tails of a pair 
of mice to see whether their young were born without 
tails. Instead of ‘‘thinking’’ how heredity might 
work, Weismann, like Columbus, sailed into the facts. 
The little mice were born with full-length tails, which 
were promptly amputated. The whole litter of this 
second generation was carefully brought up and al- 
lowed to breed together. All of the third generation 
were born with normal tails, which were at once am- 
putated. Their young of the fourth generation still 
failed to acquire taillessness, and their caudal equip- 
ment was cut off. There was no inheritance in the 
fifth or the sixth or the seventh generation; there was 
no slightest evidence that acquired characters can be 
inherited. The experiment was continued for twenty- 
two generations, and the last litter of mice had tails 
just as long and perfect as the first. The 1,592+ bodies 
of the twenty-two generations were preserved in al- 
eohol and are to-day a monument that marks a turn- 
ing-point in our ideas about heredity. 

The second chapter of the mouse-tail story is as 
significant as the first. When Weismann published 





#Virchow. See Weismann, The Evolution Theory, II, 64, 
|  tHerbert E. Walter, Genetics. 


HEREDITY 113 


his result, the scientists did not credit his report as 
truth simply because it was to be found in print. Be- 
fore they believed it they repeated the experiment to 
see that it was correct. Reverend professors in sev- 
eral European laboratories devoted themselves to am- 
putating tails of many successive generations of mice 
and rats. Not one of them found any proof that ac- 
quired taillessness could be inherited. Since that day 
no one has found any such proof, and now the scien- 
tific world has abandoned as unproved the idea that 
any sort of bodily mutilation can be inherited. 

This change of opinion is not founded on logic. So 
far as logic goes, we could reason that the amputation 
of a left leg would give the body a shock, that this 
shock might be transmitted to a germ-cell, and might 
there kill that part of a chromosome that was commis- 
sioned to build the left leg of a child. Nature might 
have made the reproductive machinery in that way. 
But she did not. No credible case has ever been found 
of a bodily injury being transmitted to offspring. 

Yet some cats are born without tails. Why? Be- 
cause the chromosomes in the single cell where their 
life began had no tail-making apparatus. The young 
of Manx cats and wild bobcats have no tails because 
those races are tailless; none of their kittens can have 
a tail unless some disorderly chromosome varies so 
much as to form one. On the other hand, every mal- 
tese cat or tiger must inherit one unless some chro- 
mosome,* by a freakish variation, fails to provide it. 
All depends on chromosomes. If for a century breed- 
ers should cut off the tails of bull pups or clip the 
ears of fox-hound pups, the heredity would not be 
affected; the chromosomes continue, undiscouraged, 
to make the same long tails and ears. Although aristo- 





*Of course monstrosities may sometimes be caused by faulty devel- 
opment in later stages of the embryo. 


114 EVOLUTION FOR JOHN DOE 


cratic Chinese women have deformed their feet by 
binding them in every generation for two thousand 
years, the child that is born to-day has normal feet, 
formed according to the pattern that chromosomes 
faithfully follow. 

That is the business of the germ-cell—to reproduce 
the ancient model. Though there is always some slight 
variation, and may occasionally be a big one, yet the 
descent always tends to persist unchanged. 

If the chromosomes that formed a certain man 
unkindly gave him a deformed joint at the base of his 
thumb, they may pass on the bad trick to the next 
generation of chromosomes, which may follow the 
new model, and so a son may inherit the deform- 
ity. But if the man slashes the thumb with an ax, 
the wound produces no effect on the chromosomes of 
his germ-cells, and the big scar can not be inherited. 

You may plant big potatoes in poor soil and dig 
small ones; then for a dozen more seasons you may 
plant the descendants there and find them always 
small. But plant the next generation in good soil; 
you will have the same large ones with which you 
started. If a quick-growing young pine tree is trans- 
planted to the top of a rocky mountain, it will become 
small and wizened, leaning away from the prevailing 
wind, unable to grow an inch a year in height; and 
the seeds that sprout from its cones in that neighbor- 
hood will form dwarfed and distorted trees. But the 
chromosomes have not been made correspondingly 
lopsided or shriveled. If you plant one of the seeds 
in good lowland soil, it will spring into straight and 
prosperous growth. The ‘‘environment’’ on a moun- 
tain is unfavorable and will alter every generation of 
trees that grow there. 

Suppose that you captured an owl, a flesh-eating 
bird, and fed it on grain, as a famous English phy- 


HEREDITY 115 


sician once did; if you could keep it alive on that diet, 
its stomach might be somewhat altered after a couple 
of years. But when the owl laid an egg, the chro- 
mosomes would be the same unchanged mechanism, 
and would proceed to create exactly the sort of stom- 
ach with which the parent was born. The character 
of grain-eating—like the dwarfing of the pine tree— 
is acquired by the body, and a change of that sort has 
never been known to be inherited. 

That word ‘‘acquired’’ is often misleading. We 
usually think of some ambitious or aggressive act 
when we hear it, such as ‘‘acquiring a lot of money, 
acquiring a big reputation.’’ But there is nothing 
aggressive in the technical meaning. A plant or ani- 
mal does not make any effort to get hold of a charac- 
ter. By some accident or disease, by some action of 
climate or food or mental stimulus, a change is forced 
upon it by an outside influence. And this change is 
always in the body-cells—in the muscles or bones or 
nerves or membranes. 

Within all this aggregation of body-cells lie the 
germ-cells, very distinct and leading a very separate 
existence. They were set apart when the egg began 
to develop. Near the beginning of every person’s 
life the germ-cells for forming the next generation 
were set aside, in a secure place, where they could lie 
dormant until the body had grown to maturity and 
had set them in action. From that early moment of 
embryo life on to the end the germ-cells are beyond the 
reach of any ordinary outside influence.* No specific 
character can be forced upon them. 

Nowadays it is known that some bacteria are so 
small as to be able to reach the germ-cells and affect 

*The paragraph does not mean that germ-cells can not be affected 
in any way through the body; it means what the last sentence says— 


that no corresponding, heritable variation can be induced in the germ- 
cells by an outside influence. 


116 EVOLUTION FOR JOHN DOH 


them. We know, for instance, that the spores of a 
silkworm parasite penetrate eggs that are still within 
the caterpillar’s body, develop with the embryo, and 
so afflict the young with the disease. The germ of 
syphilis is so small that it may be transmitted in the 
same way. Yet even such cases are not inheritance, 
because they are influences from outside the germ- 
making apparatus. Beyond that moment when the 
original cell has divided, the individual has begun its 
separate life, and any change is an acquired character. 
This is not a matter of definition or stickling for a 
point; it is a fundamental distinction. Any one who 
cares to keep his eyes on the chromosomes will see it. 

In no ordinary case can disease or alcoholism or 
any form of debility acquired during an individual’s 
lifetime be specifically inherited by its offspring. And 
any men who build theories on a few apparent excep- 
tions must nowadays speak in different terms from 
those which were used thirty years ago. No modern 
scientist claims more than this: that a profound 
change in the body-cells might be communicated to 
the germ-cells, and so might stimulate or interfere 
with them. Thus an outside influence might throw 
the chromosomes into confusion and cause defective. 
work. Or if a chromosome is carrying two patterns, 
the first of which would normally be suppressed, an 
outside influence might be a disturbance that could 
cause that first one to develop, or it might act as a 
kind of trigger that would throw into gear an old pat- 
tern which had lain dormant in the chromosomes for 
hundreds of generations. But no outside influence 
can remodel the machinery or add a new part. No 
outside influence can produce a corresponding effect 
in the germ-cell, any more than the carbon on a spark- 
plug can make a carbonic engine. Darwin expressed 
the effect of an outside influence thus: ‘‘The nature 





Two examples of Nature’s experiments in bone-making. The hero-shrew, above, 
has a spine that looks like lace-work; the pigmy armadillo has a dirt-rammer at 
the base of its spine. 


‘TUNOSN]T Weoley 
ay, 98 4YSnoq oq 0} Ysvg ay, fo sjowwy ‘seony “y “WZ Aq Yood e[qeryer ‘paotid-moy, ‘pozerysni[t “surureytezua 9y4 
gos ‘somnjord Jo sased xIs 4XoU Ol} UL UMOYS Sia}sTOM JouTyXe oY} JO yWourdo[oaop oY} FO puB “iNVsOUTP peuLOYy Sty} FO 
qunoosse UB IOg ‘OSB Sivek UOTT[TU APxIS oWOS ‘sdoyRdooLLy, FO pRay oy}. FO doz oy} 4B SuTYRU-oNOg UI quowttedxe UW 





HEREDITY 117 


of it is perhaps of no more importance than the na- 
ture of a spark in determining the nature of the 
flames.’? Darwin was always skeptical about the in- 
heritance of acquired characters, and did not base his 
theory on it,* though he is often accused of doing so. 

The great body of evidence coming from the lab- 
oratories to-day shows how independent germ-cells 
are of the body-cells, what a detached life they lead, 
and how they work by a routine process. Any one who 
could for a few minutes look with his own eyes at the 
‘‘mechanism of heredity’’ that Professor Morgan of 
Columbia has demonstrated by experiments and 
studied under his microscope would never again be 
hazy about acquired characters. This man—and doz- 
ens of other recent investigators—has taken the 
guesswork out of chromosomes. What Darwin did not 
live to see, what Weismann saw dimly and speculated 
about, he now pictures for us in books{ that all may 
read. In nuclei not one-ten-thousandth of an inch in 
diameter he has seen the operations of the beginning 
of a new life ina cell. He has seen chromosomes in- 
tertwine, exchange parts with each other, and move 
asunder; he has seen them solitary and in equal pairs 
and in unequal pairs; has seen them split apart; has 
watched their actions vary with temperature and ob- 
served their regularity. He has seen the chromosome 
that determines whether the new animal shall be male 
or female. 

Aljl this 1s wonderful enough, but he has gone much 
farther. He has proved with painstaking care that 
certain parts of certain chromosomes have their par- 
ticular jobs. (These parts are called ‘‘genes.’’) He 
has been able to predict from the way chromosomes 


*See Chapter XXIV, Section V, for quotations. 


tThe Mechanism of Mendelian Heredity and The Physical Basis 
of Heredity. 


118 EVOLUTION FOR JOHN DOE 


join with each other whether the egg will develop into 
an insect with shield-shaped wings or forked wings, 
with white eyes or red eyes. He has found that some- 
times the work of many genes is necessary to make 
some one slight character. After breeding millions 
of little fruit-flies through hundreds of generations 
and tabulating the results, he and other investigators 
were able to make a map of the main parts of the 
ehromosomes, which were shown by four parallel lines 
in a diagram. Well may an admirer of their work 
say of these lines, ‘‘It is doubtful if in any book there 
may be found four straight lines that mean so much.”’ 

No scientist of standing to-day can conceive, in 
view of all this exact knowledge of how chromosomes 
behave, that any particular change made in any crea- 
ture’s body during its lifetime can be passed on to its 
offspring. Heredity is now known to be a matter of a 
succession of germ-cells. They are the means—the 
only means—of carrying on the pattern of life from 
one generation to the next. Every germ-cell is born 
directly from a previous germ-cell, of which it is a 
reproduction. There can never be any gap in the suc- 
cession. Here is a stream of life that has flowed 
continuously from the first nucleus to the last. It is 
this unbroken stream of heredity that nature cares 
about. The trunks of trees and the bodies of sharks 
and moose are only contrivances to keep the stream 
flowing, only a series of reservoirs for germ-cells, a 
series of homes in which germ-cells may be protected 
until they can reproduce. 

Picture to yourself a stalk of corm that was 
growing by a New England lake when Athens was 
young. Its sturdy stalk mounted, its splendid 
leaves were thrust out, and its roots spread vigor- 
ously. When its whole body had developed, it 
flowered at the summit in a tassel, producing in- 


HEREDITY 119 


numerable minute grains of pollen. Hvery one of 
these was a plan of the entire plant—root, stem and 
blossom—with provisions for rebuilding an entire set 
of the hundreds of millions of varied sorts of cells. 
Below the tassel had grown another set of flowers 
(clustered about a cob and covered by layers of 
husks), each of which sent out a long thread to the 
end of the cob; there the threads emerged from the 
husks and hung in a silky cluster. On to each fell 
pollen grains. The fortunate one in each case found 
its way to the hollow core of the thread and descended 
the whole length, to where at the base an egg was 
awaiting it, an egg that also had provisions for the 
whole organism of a stalk of corn. Into this it made 
its way, and the two cells combined into one. The new 
cell divided, mingling the chromosomes from the two 
parent cells and sending equal parts to each of the 
new ones. Each of these in the same way divided 
equally its inheritance. From four to eight to sixteen 
to thirty-two to the end there was the same equal di- 
vision of the inheritance. Thus was formed an em- 
bryo of a new stalk of corn. This was the treasure 
for which the plant had labored. The rest of the 
plant’s life was devoted to building around the em- 
bryo a store of rich nourishment for its next stage 
of life. The seed was complete—a kernel of corn. The 
parent died. 

Through the winter the embryo slept. Next spring, 
when warmth and dampness had stimulated it enough, 
it resumed the multiplying of its cells, each of which 
received that equal inheritance from tassel and silk— 
each one of the vast aggregate that was to labor un- 
derground and in the pith and in the sharp edges of 
the leaves of the new plant. All their combined labor 
through the second summer was for one result—to 
build a home for the germ-cell that was to continue 


120 EVOLUTION FOR JOHN DOE 


the stream of descent. This was a part of its parent 
cell, a veritable piece of it, and it kept the unbroken 
stream of life flowing through the summer of plant 
growth and through the winter of plant death. 

Its own self was in the tassel and the silk of the 
third summer, and of the fourth. And so long as that 
species of maize lives, every kernel will be a link in 
a continuous chain of germs back to the beginning of 
the species. And the first cell of maize that ever lived 
must have been born directly from some previous cell. 
There never has been—there never could have been— 
any gap of a single link in the succession of cells from 
the beginning of life on our globe. That is the ‘‘germ- 
plasm stream.’’ That is heredity. 

It is the force that tends to make life durable, per- 
sistent, unchanging. No wonder that Weismann ex- 
claims about ‘‘the enormous duration of the constancy 
in a species.’’ He was speaking of some butterflies 
that have maintained, in an unchanging form, a germ- 
stream for fifty thousand years. Even that period is 
short compared with another that we have heard of 
in a previous chapter—an unchanging succession of 
germ-cells in a tree for several million years. One 
genus of little bivalves (Lingula) has lived almost un- 
changed through nearly the whole geologic record 
to this day—so long a duration that estimates of it 
vary from twenty million years to two hundred mil- 
lion. Heredity always tends to preserve the same 
forms forever. 

The persistent power of the current of sameness 
may seem even more striking if we turn from the in- 
conceivable stretch of ages to some petty subject, say 
pigeons. These have been domesticated for several 
thousands of years and have varied in the most ex- 
treme, sometimes outlandish, ways; but if we mate 
two of the artificial varieties, we shall see young that 


HEREDITY 121 


are like their ancient ancestors of Asia. Before the 
Babylonian Empire arose, there had been set up in 
the chromosomes of the wild rock-pigeon a design for 
bodies of a certain size and shape, covered with feath- 
ers in a certain pattern; and all the while they have 
carried it in the germ stream, latent and concealed; 
now when they are disturbed, back they go to the 
model that is native and deep founded. Hiven the use- 
less hairs on our arms are always set according to a 
certain ancient, established pattern. 

Do you complain that this is confusing? Do you 
find fault because the chromosomes are one minute 
described as unchanging, and in the next minute as 
ever-changing? You well may complain, for the state- 
ments seem contradictory. The contradiction, how- 
ever, is the fact of nature. Chromosomes have those 
two opposite qualities. On the one hand they are 
never absolutely precise and may vary most wildly; 
on the other hand they may return from their fluc- 
tuations to their original design and reproduce it un- 
swervingly for ages. Their variation is a fact, which 
was exhibited at length in the preceding chapter. 
Their unswerving fixity for long periods is equally a 
fact. If a paleontologist takes a rapid glance at the 
record of all life for fifty million years, he is im- 
pressed by the variation; and yet he is the very man 
who can give us the most striking examples of un- 
varying heredity. If a naturalist observes poplars 
and swallows from year to year, heredity seems the 
conspicuous feature; and yet, if he is careful enough, 
he will see perpetual variation. These are two insep- 
arable truths, as opposite as the foundation and the 
roof of a house—and not any more at odds with each 
other. 

They will be reconciled in the next chapter, on 
Selection, When we have understood each truth sep- 


122 EVOLUTION FOR JOHN DOH 


arately, and have then understood how they cooperate 
with each other, we shall have the secret of evolution. 

Before we conclude the chapter we should remove 
from our minds a doubt that is lurking there, ‘‘ How 
can it be,’’ our skeptical brain keeps asking, ‘‘that 
the intricate pattern of heredity for a whole animal 
is carried in the minute space of the chromosomes?’’ 
We can not conceive that the whole of a big organism 
is all represented and provided for in some micro- 
scopic beads on a thread. 

The only trouble is with our brain, which is to the 
last degree gigantic and gross in its ideas. We can 
not realize how huge and crass are our notions of mat- 
ter as compared with what 1s known in the modern 
laboratory. If we adjust our brain to the facts of 
recent physics, a chromosome will seem as big as a 
palace, a roomy place for the architects of anatomy. 

Begin the adjustment by picking up a ruler and 
seeing how small a distance an eighth of an inch is. 
Take half that distance, not a pinhead’s width, and 
imagine a cube each side of which is one-sixteenth of 
an inch long. Does it seem a small space in which to 
stow a life-making apparatus? Only because we are 
like the towering creatures that grinned at the tiny 
six-foot Gulliver and wondered how blood could cir- 
culate in so small a heart as his. They were only six 
times as tall as Gulliver. If they had been a thou- 
sand times taller still, they. could barely have seen the 
speck of a human being and would have found it im- 
possible to believe that in him were capillaries and 
brain-cells. They would not have had imagination 
enough. If we can be unlike the giants and ean stretch 
our minds into the realms of the microscope and be- 
yond, we shall have no more skepticism about the 
capacity of a chromosome. 

Descend into this sixteenth-of-an-inch cube, which 


HEREDITY 123 


we will suppose is filled with human blood; become, 
as you were in the clover leaf, one-ten-thousandth of 
an inch tall. You are in a whirling world of twenty 
million disks. Most of them are of a yellow color, 
(the ‘‘red corpuscles’’), with a diameter three times 
your height; each is an elaborate chemical apparatus 
for distributing oxygen. It is a large coarse structure. 
If it were a person, it could not begin to see a molecule 
of the protein in its system, for it 1s twenty-three 
thousand times as wide as that molecule.* It is mass- 
ive and coarse and of vast size. If we wish to descend 
in matter until we can see something that is slightly 
refined, we must grow very, very much smaller, until 
finally we are far within the red corpuscle, and a 
molecule looms large before us. Even here we are 
disappointed, for we perceive that the molecule is 
massive and coarse, made up of swirling atoms. At 
this stage of our journey we are prepared to believe 
that the mechanism for making an elephant might 
easily be arranged for in one molecule. We must re- 
duce by a tenth until we can pay proper attention to 
an atom. Lo and behold, it is massive and coarse! A 
physicist has written about Exploring the Atom, and 
if we wish to explore we must reduce our size, and re- 
duce, and reduce. It is a long stage, this last one. So 
extended is the great reach of space before us that we 
are glad we are safe at the circumference of the atom, 
and not winging our way into its fathomless depths. 
Its diameter of one-three-hundred-millionth of an 
inch is now an illimitable field for our straining eyes. 
At length we see the electrons darting with fearful 
speed in their assigned orbits within the atom. And 
they have plenty of room. They are as remote from 
one another in proportion to their size as the earth is 


*According to Comstock and Troland’s entertaining account in 
The Nature of Matter and Electricity. 


124 EVOLUTION FOR JOHN DOE 


from the other planefs. The mind can endure no more. 
It reels as it tries to apprehend the spaciousness of an 
atom. 

When a person returns from such an expedition 
to this our region of human sensations, he has left 
his skepticism behind. He can exclaim with Hamlet, 
‘Oh, God! I could be bounded in a nutshell and think 
myself a king of infinite space.’’ Any space that our 
mountainous minds can conceive is more than is 
needed for the mechanism that nature contrives to 
carry on heredity in chromosomes. We gain in an- 
other way by such an expedition: we no longer object | 
to calling chromosomes a ‘‘mechanism.’’ That is an 
ugly and untruthful word if it suggests the coarse- 
ness of steel and steam; but now we know that it is 
only the organized powers, working by nature’s laws, 
which convey from generation to generation, in the 
spacious chambers of a chromosome, the hereditary 
characters of a race of plants or animals. 


CHAPTER IX 
NATURAL SELECTION 
I. Sifting Out the Unfit 


In a school of salmon running up a turbulent river 
and leaping waterfalls to spawn there are some that 
were born too weak for such a severe test. These 
can not endure to the end, and so they fail to propa- 
gate. If a hundred seeds from spruce trees are lying 
in the soil of a vacant spot in the woods, they are not 
all alike; some have a weaker apparatus in their nuclei 
than others. When these sprout, they are doomed to 
failure; for the trees from other seeds can put out 
roots and climb for sunshine somewhat faster. So 
always in the struggle for existence: weakness is not 
excused and can never endure; it disappears. 

Of all the young of any species born on a certain 
day a few are exceptionally well fitted to survive; 
some are moderately fitted, and many are not quite 
well enough fitted. Of course there will be casualties 
that come to the well-fitted and the ill-fitted alike; 
lightning may destroy the strong and the weak in- 
discriminately, and enemies may sometimes have 
better luck against the strong. But otherwise, and in 
the main, variation has doomed a few to survive 
through a long fight, and many to be emancipated by 
early death. Survival or disappearance is principally 
a matter of variation®* in chromosomes—often a very 

*For the kinds of heritable variations (the ‘‘recombinations’’ and 
the ‘‘mutations’’) see Chapter XXIV, Section III, 

125 


126 EVOLUTION FOR JOHN DOE 


slight difference. <A little more length of wing, a 
little less weight of bone, a little—only a little—larger 
breast muscles, may be the difference between life 
and death in securing food. A slightly thinner shell 
of a seed may mean that the germ can sprout a little 
earlier, and so get the start of others and survive 
them; or it may mean that the germ can not survive 
the rigors of winter, and so will perish. 

How shall a well-fed, office-bred American under- 
stand this? He was never hungry in his life—not 
with a fierce, compelling hunger; his main concern 
with food is to refrain from eating too much of it. 
He must stretch all his powers of imagination and 
sympathy if he would understand what variation 
means in the competition for food. He would have 
seen an illustration if he had gone on an army trans- 
port, during the Spanish-American War, from San 
Francisco to Manila. For thirty days the steamer 
plowed her way across the Pacific. In her wake were 
some gulls that needed food, more than they could 
find in the crowded competition of San Francisco 
Bay. They were not enjoying travel for travel’s sake; 
they were struggling for the scraps that were thrown 
from the cook’s galley; and all their strength was 
needed to survive. The gull that could endure for 
only twenty-nine days would perish. 

We know by actual measurements that all birds do 
vary in structure and power. ‘‘A variation of from 
fifteen to twenty per cent. may be ordinarily expected 
among specimens of the same species and sex, taken 
at the same locality.’’* And we know, furthermore, 
that variations much less than that may preserve from 
death. A captain of a ship in the Atlantic once made 
these two entries in his log when he was one hundred 


*Quoted in Wallace’s Darwinism, from which come the data for 
this paragraph, 


NATURAL SELECTION 127, 


and sixty miles from land: ‘‘A great many small 
landbirds about us; put about sixty in a coop, evi- 
dently tired out. . . . Over fifty of the birds died, 
though fed.’’ They had been blown to sea while mi- 
grating, and only one-sixth of them had power to 
survive. <A flock of one hundred and thirty-six spar- 
rows, driven by a hard wintry gale, exhausted and 
numbed with cold, were once taken into a laboratory 
of Brown University. In spite of the best care, sixty- 
four died. Accurate measurements were made of the 
living and the dead; tabulations showed that the dead 
were (1) slightly larger, (2) slightly heavier, and 
(3) had slightly shorter breast-bones. That is, those 
birds which had weaker breast-muscles in proportion 
to their weight could not endure the storm as the 
others did. In this case the difference between life 
and death was a difference of only one and one-third 
per cent. in the proportions of parts of the anatomy. 
Such variations, and much greater ones, are always to 
be found in a flock of wild birds; the favorable varia- 
tions will, in the long run, survive. 

This fact that only the best adapted plants and 
animals can live is called Survival of the Fittest. Or, 
since nature seems to ‘‘select out’’ the unfit and 
remove them from the struggle, the process is fig- 
uratively called Natural Selection—the name that is 
now in more common use. It is a name that misleads 
the unwary.* Nature is not a breeder and does not 
‘“select.’? What actually happens is that the less fit 
do not survive, while the more fit, or the fittest, do 
survive. 

*Darwin coimed the phrase as a kind of parable, in which nature 
is represented as ‘‘selecting’’ the best variations, as being a kind of 
breeder. Though he defined it carefully as including both ‘‘ preserva- 
tion and destruction,’’ his parable has always confused literal minds. 


It misled John Burroughs so completely that he accused Darwin of 
being anthropomorphie! 


128 EVOLUTION FOR JOHN DOH 


What will be the result of natural selection as it 
operates unswervingly through the centuries, always 
removing some variations and leaving others to repro- 
duce? The answer is not easy to read in nature, because 
most of the results are brought about very slowly and 
were fixed long ago. But we can see an illustration 
of one part of the process by watching another kind 
of selection in artificial conditions. We can see how 
breeders of animals and growers of plants select varia- 
tions for a series of generations. They work on a 
principle opposite to nature’s, but they can give us 
the clue to natural selection, just as an artificial 
electric spark in a laboratory gives the clue to under- 
standing a stroke of lightning that is formed by nature 
in a very different way. 

A. breeder selects variations for his human purpose 
—often a freakish one—of securing a result that has 
more meat or more expanse of petals. What we can 
see in his process is a series of variations that are 
inherited and that result in a different kind of crea- 
ture. That is what we need for an illustration, because 
that part of the process is what occurs in nature. But 
we can use nothing more. The breeder and the 
breeder’s purpose are utterly different from nature. 


II, Artificial Selection: Preserving the Unfit 


The wild rose of Scotland has only one set of 
petals, arranged in one flat disk; it is a single flower. 
The idea once occurred to a Scotch florist that this 
blossom would be more beautiful if it had more petals, 
if it were double. His way of operating is an example 
of all those ways in which plants and animals can be 
adapted to man’s fancy if the unfit are allowed to 
survive. 

He did not begin by tampering with any seeds or 


NATURAL SELECTION 129 


blossoms; he did not do anything to any plant. He 
simply examined a great many flowers. Of course 
he found that heredity had been making the blossoms 
all very much alike; all were single and five-petaled, 
similar in size and color; he might have looked at 
thousands of blossoms before finding a variation from 
this pattern. But he knew that variation is bound 
to occur and is bound to be discovered by any per- 
sistent searcher. He persevered till he found a 
blossom that had one extra petal, which was growing 
inside of the regular five. This sporting flower he 
marked, and in the following fall preserved the seed- 
ball. So much for the variation part of the program. 

The florist knew that any such variation, even if 
it is abnormal, may be inherited. Next spring he 
planted all the seeds, and in the summer scrutinized 
the flowers. Three of them had inherited the extra 
petal. All the normal blossoms he destroyed, and 
next spring planted the seeds from these three un- 
natural ones. Ten blossoms inherited the extra petal. 
To an impatient man this is not much of a result for 
three seasons’ work, but the gardener was quite con- 
tented, knowing nature’s ways and knowing that it 
takes a little time to break up the habits of long ages 
of inheritance of what is adapted to the struggle for 
existence. Next year a number of his blossoms 
showed a whole extra row of petals, and the doubling 
was under way. Within ten years he could show in 
his garden a flower that had six rows of petals. In 
so short a time had the pattern of the chromosomes 
been altered and a new one substituted. The double 
flower now had a changed heredity apparatus with 
respect to the number of petals; this followed the new 
model and has regularly produced, generation after 
generation, to this day, roses with many rows of 
petals, 


130 EVOLUTION FOR JOHN DOE 


But it is artificial, made by the fostering care of 
man. If it were turned out to shift for itself in 
nature’s struggle for existence, it would probably 
prove unfit and would perish. 

That process of making a new kind of blossom 
is always the course of artificial selection. Man can 
not begin the operation. Nature has to make the 
beginning. In some egg it happens* that the chromo- 
somes are somewhat erratic, that they depart from 
the ordinary model. Why they vary no scientist 
knows—possibly no scientist will ever know. We 
can see the effects and can take advantage of 
them, just as an animal trainer can see the effect of a 
whip or a reward of food, though he never expects to 
know what makes the cells in the animal’s brain be- 
have as they do. We know that there is a complicated 
mechanism in chromosomes which never works with 
absolute precision, and we can see the results of their 
varying. That variation arises, suddenly appears, in 
a flower or a nose or a leg. When it has appeared we 
know that it is an alteration in the germ-stream of 
life, and so can become an inherited character if it is 
carefully preserved. We can thus manipulate hered- 
ity. This finding of a variation and then developing 
it by preserving characters that are adapted to man’s 
wishes is artificial selection. 

The human race was practising selection before 
the dawn of history. The earliest lake-dwellers in 
Switzerland selected variations in wheat and kept alive 
artificially a plant with plump grains that could not 
maintain itself in the struggle for existence. The 

*Of course nothing can ‘‘happen’’ without a cause. Every 
‘fehance’’ variation was produced in accordance with fixed natural 
laws. But we know nothing about the cause. When a scientist uses 
such words as happens or by chance or fortuitously, he always means 


‘*produced by unknown eauses.’’? See Section V of this chapter for 
a discussion. 


“LOY YIM poAtosotd atom Cunod ULoquN Lo JO [BIAS {Suo] Joos OE Jnoge ‘ajvutaf B st UoturDods aI, "SE MOU AUBULIOD 
OLOAL WMS 0} Posh PUB UBIO OY} UL oJl[ LOF poJdUpe ‘ovVyA ULopoul oY} ay] ‘awBooq ‘snanvsoayzYyoT uv ‘opydat sip, 





‘WaYe} ST Spuose[ osoy} TOF WOTPVUIAOFUT oY} FO OOS YoryM WOT ‘wornjoas ovwvb1C 
U 


[ 
aTqeimtuipe Ss. [IN] “SG “Y Ul UoaTs st ‘suoTzRIysNT[t snordods yyrm ‘so[tydat oY} [[B FO WOTNTOAD FO LopLO oY} FO JUNO 


ny “uo nyssvoons Jou sVeM Yorym ‘outds ot 0 JUaUIdOTOAOP ShorjsuowW B YM ‘sotZdet ATIBe oY} JO ou 
[Ug + [OF [ory I 1} JO 4 f I l 


GOEL 93044 
HOE SB Yas, 





NATURAL SELECTION 131 


earliest North American Indians must have hved on 
the small kernels of a wild plant, in which they de- 
tected small variations; they selected the larger 
kernels for planting and developed ‘‘corn.’’ So long 
continued was the selecting in these cultivated cereals 
and so far were they trained away from the original 
forms that now the botanist can not tell from what 
wild plants they descended. And the variation is 
not at an end. To-day more than ever the agricul- 
turists are noticing variations, selecting them for food 
values, and shielding them from the struggle for 
existence. 

All our grains have been found by the same pro- 
cess, all the vegetables in our gardens, all the fruit 
trees, all the cultivated vines, all our beautiful garden 
flowers. Everywhere in the world to-day men are 
looking for variations as if they were prospecting for 
gold. They can no more make variation than they can 
create a precious metal; they can only seek for the gifts 
which the chromosomes have created here and there. 
To be sure, a gardener who wants variations in a wild 
plant may stimulate them by putting the plant in 
richer soil; but this is only hastening the variations 
or setting them free. Nothing but chromosomes can 
originate a variation. The first step of all selection 
in garden vegetables or trees or flowers must be to 
search for what some unknown power has made. A 
variation may be a great leap to something startlingly 
new—like the bellflower apple—or it may be an 
infinitesimal step; but, large or small, it is caused by 
some sort of change in the chromosomes of the germ- 
cells. 

When variations are closely observed in a plant 
and carefully selected through many generations, they 
may be led into extremes of size and shape. The 
species of one genus (Brassica), which still flourish 


132 HVOLUTION FOR JOHN DOE 


in their wild state as insignificant little weeds, have 
been worked into a great variety of vegetables. One 
of them has been developed into a cabbage, the head 
of which is unlike anything in nature, and into a 
cauliflower, and into Brussels sprouts. A second 
species has been selected along two lines: at the end 
of one is the turnip root, and at the end of the other 
are the oily seeds of the rape. A third species is 
mustard. 

We all know what selection can do with flowers. 
It brings a yellow single flower from Brazil to France, 
doubles it, increases its size, and gives it all the forms 
and colors that are annually shown in the Bronx Park 
exhibits of dahlias, at the last one of which ‘‘Uncle 
Sam’’ was pink in color and nine inches in diameter. 
Artificial selection takes a Chinese daisy and enlarges 
it to a mass of yellow bloom, a chrysanthemum, twenty 
inches across. 

Cabbages and chrysanthemums are adaptations to 
the wants of man, but not to the struggle for existence. 
They are flabby unnatural plants that can live only 
when they are removed from the competition of 
nature—from natural selection. 

As with plants, so with animals. Before history 
began, men had been selecting, almost unconsciously, 
the differences in dogs. By the time the records open, 
men had many kinds, most of which could not have 
survived in the struggle for existence. There were 
slender hounds for speed and silky ones for pets. Man 
has manipulated the race as if it were so much clay, 
fashioning now a little helpless, hairless creature, now 
a squatty fighter all front legs and jaw, now a big 
friendly brute with woolly coat, otter-hounds that have 
developed quite a web between their toes, a collie that 
has become highly intelligent, a stupid Chinese dog 
that is fed on vegetables and is used for food. We can 


NATURAL SELECTION 133 


set no limit to the molding of animals that may be 
possible in the future. Horses have been shaped into 
grayhound forms for racing and into almost elephan- 
tine forms for hauling drays. Pigeons have been 
bred with monstrous tails, with enormous ‘‘pouting”’ 
breasts, with long wattled noses, with beaks so short 
that the young can not peck their own way out of the 
shell. Pigs have been made so fat that they are no 
longer like real animals, but are a sort of meat factory 
on legs so short as hardly to keep the body off the 
ground. Man has gone even farther than this in op- 
posing the course of nature; he has preserved for his 
- amusement demented mice that spend their lives in 
whirling round and round; he has fostered disordered 
birds that ‘‘tumble’’ in the air. 

Not all of these artificial creatures are weak. 
Darwin warns us that ‘‘we must not overrate the dif- 
ference between natural species and domestic races; 
there is no palpable difference between them... . . 
Domesticated races propagate their kind far more 
truly, and endure for much longer periods, than most 
naturalists are willing to admit.’’ The bull-dog and 
the game-cock are certainly strong, and some culti- 
vated plants are hardy if left to shift for themselves 
—buckwheat, for instance, will choke out morning- 
glories, a most powerful weed. But the bull-dog could 
not run down prey nor the game-cock scratch for food 
with his spurs if they were turned out to compete for 
a living in nature. It is not a matter of ‘‘strength”’ 
or ‘‘weakness’’; it is a matter of being adapted, 
fitted. The strength of the fiercest bull-dog may not 
fit him to survive in nature; whereas the flabby 
‘‘weakness’’ of a parasite may fit it admirably. to 
survive. 

All artificial selection—though opposite to nature 
in purpose and result—shows strikingly one element 


134 EVOLUTION FOR JOHN DOE 


in natural selection: that certain types of variations 
are inherited, and that the inherited characters can 
increase by further variation, and that by selecting a 
series of such inheritances a plant or animal can be 
gradually altered into a new form of life. Hvery 
organism is plastic material that can be molded by 
selection. But selection merely takes what nature pro- 
vides in the form of variations. It creates nothing 
itself. | 

In the short time that man has been systematically 
altering natural forms he has never made such trans- 
formations as putting horns on pigs or shifting eyes 
to shoulders; but within limits he can decide what he 
wants and can then build to attain it. He can shape a 
rooster’s comb, or the shoulder or the eye of a cow; 
he can alter the grain of the meat in a hog or re- 
model a canary’s head. <A successful breeder has a 
‘“nrophetic vision,’’ and that which he foresees he can 
make by selecting the variations that germ-cells create. 

Artificial selection is not limited to animals that 
have been long domesticated; it is a process that is 
always seen when man breaks into the struggle for 
existence at a point where nature was never interfered 
with before. One experimenter* bred some little fruit- 
flies that showed slightly abnormal veins in their 
wings, removing from each generation those that were 
normal and allowing the abnormal to breed. In the 
sixteenth generation all the young were born abnor- 
mal, though in nature only one in three hundred is 
abnormal. Then the experimenter reversed the pro- 
cess. Starting with an abnormal pair and removing— 
‘‘selecting out’’—all the flies born with abnormal 
wings, letting those that were normal breed, he pro- 
duced a sixth generation that was one hundred per 


*Frank E. Lutz, Carnegie Publication 143., This report is illumi- 
nating and significant. 


NATURAL SELECTION 135 


cent. normal. By selecting for twenty-two generations 
he had made a round trip in variation. 

When successive generations of young flies are 
carefully observed, many kinds of variations are seen: 
some have limber wings, some have short wings, some 
have poor eyes. The new forms are not caused by 
artificial conditions, but are such as frequently appear 
in nature. They are healthy and will breed if they 
receive food. Why, then, do such forms never breed in 
nature? ‘‘Wild rabbits,’’ says Wallace, ‘‘are always 
of gray or brown tints, well suited for concealment 
among grass and fern. But when these rabbits are 
domesticated, without any change of climate or food, 
they vary into white or black, and these varieties may 
be multiplied to any extent, forming white or black 
races.’? These white and black colors are not new 
characters caused by putting wild animals into pens; 
they are variations that continually occur in nature. 
Why, then, are white and black rabbits never found 
in nature? 

Guinea-pigs normally have three toes on each hind 
foot, but once in a great while a specimen is found 
that hag four toes on one hind foot. Such a rare ani- 
mal has been bred; all the offspring that did not in- 
herit the fourth toe were selected out; all that did 
inherit were allowed to breed. In the fifth generation 
ninety-seven per cent. of the young had four toes on 
each of their hind feet.* Why has no such race de- 
veloped amid the struggle for existence? 

The variations that have been described occur re- 
peatedly in nature, but regularly disappear. Does this, 
then, mean that nature never tolerates variations and 
never practises selection? The answer is in Section 
ELT: 


*W. E. Castle, Carnegie Publication 49. 


136 EVOLUTION FOR JOHN DOE 


III. Natural Selection: the Survival of the Fittest 


The man who made ‘‘the round trip in variation’’ of 
fruit-flies has observed in another set of experiments* 
what happens to variations in the struggle for exist- 
ence. He studied crickets on Long Island, near 
Oyster Bay, where a corps of experts work at the 
Station for Experimental Evolution. He collected 
specimens in four places: (1) on the mainland, where 
the soil was good; (2) at the base of a sand-bar, where 
the soil was poor and sandy; (3) in the middle of the 
narrow sand-bar, which ran out seven hundred yards 
into the water; (4) at the tip of the sand-bar, where 
there was no soil, but only pure sand. He measured 
on every female cricket the length of the egg-laying 
tube, the ‘‘ovipositor,’’ that protrudes, long and prom- 
inent, from the end of the body. The average length 
of the ovipositor on the mainland was eighteen milli- 
meters (eighteen-twenty-fifths of an inch); the aver- 
age length at the base of the sand-bar was nineteen 
millimeters; in the middle of the bar nineteen and one- 
half; and at the tip twenty. The varying lengths were 
neatly assorted for these small differences. Here wasa 
most curious proof that some kind of selection had been 
made—as obvious as if you should enter a room and 
find four piles of firewood neatly sorted out according 
to lengths. Such assortment could not be an accident. 
No more could these crickets merely happen to be 
arranged in groups; for the same measurements could 
be found year after year; the crickets do not migrate 
much in any season, but inhabit their regions for gen- 
erations. Some force had been selecting. It must 
have been a very discriminating force, for it worked 
with differences of one-fiftieth of an inch. 

If you asked a savage what did the selecting, he 


*Carnegie Publication 101: The Variations and Correlations of 
Certain Taxonomic Qualities of Gryllus, by Frank KE. Lutz. 


NATURAL SELECTION 137 


would reply that some spirit, some sort of intelligence, 
had been herding the crickets into bunches. But the 
Cold Spring Harbor experimenters have found no sign 
of any spirit. If you ask the first intelligent, non- 
scientific man you meet, he will probably say, ‘‘Oh, 
the rich soil makes ovipositors fat and short, while the 
sand makes them long and lean.’’ The intelligent man 
is giving the answer that seems always to spring up 
in the human mind—the idea that the environment 
causes changes and that these acquired characters are 
then inherited. Even trained minds that know an out- 
line of evolution, show a strong tendency to slip into 
the old, baseless, impossible explanation. 

Only by keeping our eyes on the chromosomes can 
we hit the truth. Of course the truth is that all such 
selection must have begun with germ-cells. The 
length of egg-layers is very variable. In other locali- 
ties crickets thrive with an implement only fourteen 
millimeters long; and where the average of the pop- 
ulation is nineteen millimeters, no two specimens will 
have ovipositors of exactly the same length. That 
variability is the beginning of the right answer. The 
next part is readily found by looking into the struggle 
for existence of crickets. In the fall they lay their 
eggs in the ground: in one locality fourteen milli- 
meters is deep enough (supposing for convenience 
that the depth of the hole equals the length of the 
egg-layer), but at Cold Spring Harbor it is not nearly 
deep enough; even on the mainland an egg buried only 
seventeen millimeters may be destroyed during the 
winter. A mother who buries her eggs less than 
eighteen millumeters may not have offspring next year. 
In the middle of the sand-bar the egg must be slightly 
deeper if it is to hatch; in the sand at the outer end 
no young will survive if the mother probes less than 
twenty millimeters. 


138 HVOLUTION FOR JOHN DOE 


The answer is complete when we inquire about 
heredity. If any germ-cell fails to produce a long 
enough ovipositor, it will not survive in daughter 
cells, in the germ-plasm of the next generation of 
erickets. Eivery mechanism that produces a proper 
length has a good chance to survive in the next gen- 
eration. All the germ-cells of the next generation 
which are true to their inheritance will have a good 
chance to survive; and all that do not follow the suc- 
cessful model will perish. The winter’s cold selects 
germ-cells more neatly than if it were intelligent. 

To be sure, there are all manner of exceptions to 
this cut-and-dried summary of a case of natural selec- 
tion: a female with a shorter ovipositor might push an 
ege deeper than one with a long tube; during one win- 
ter less depth of burial is needed than for another 
winter. We can never know all the ins and outs of 
even a simple example of the struggle for existence. 
But the principle is truly set forth. Temperature and 
soil conditions can select unfavorable variations of 
crickets, and thus gradually alter their forms, more 
surely than any human breeder could. 

Nature works surely, and in the long run works 
exactly. But in any one season selection may be very 
irregular. Some of the best-fitted animals may die by 
accident, and some of the unfit may have the good 
fortune to survive. There is no precise standard of 
what is absolutely most fit. Nature, in general, de- 
stroys those animals that are less well fitted for the 
struggle. The fact is that natural selection is ‘‘sur- 
vival of the fitter’’—it is a comparative matter. It 
may happen, also, that some weaker animals, cut off 
from competition, can survive for a longer time than 
others that are stronger but that live in fiercer com- 
petition, Allis relative. We can only say that in any 
set of conditions the animals that are more fit have a 
better chance to survive. 


NATURAL SELECTION 139 


- The impersonal forces of nature alter the dimen- 
sions of an animal in ways that are less direct 
than in the case of crickets. It was once found that 
the crabs on a beach near Plymouth, England, were 
growing slightly narrower. Careful measurements in 
hundredths of inches showed unmistakably that a 
general progressive change was going on, that some 
force of nature was selecting out the broad crabs and 
killing them. So the puzzle was: ‘‘What change in 
the environment is putting broad crabs to death?’’ 
One shrewd observer guessed that the cause might be 
an increased amount of clay in the water, for it was 
known that the working of more land up the river had 
caused more clay to be washed to the ocean, and that 
the very fine particles of the clay kept the shore water 
somewhat muddy. An experiment in a laboratory 
proved that the guess was right; for if a lot of crabs 
were kept in a tank of slightly muddy water, the 
broader ones died, No one knows the reason why the 
broad crabs can not live; their mere breadth can not 
be the cause; it happens that the broad ones are con- 
stitutionally unable to resist muddy water. Here was 
a demonstration that year after year the clay parti- 
cles from the river were removing a certain variation 
among the crabs—just as certainly and just as ac- 
curately as the temperature of different regions selects 
certain unfit crickets. If a great deal of clay had 
come down the river some spring, all the crabs might 
have perished at once. But since it increased grad- 
ually, it first selected only the very broad ones, next 
year those not quite so broad. Each year there was 
a weeding out of all crabs that varied toward broad- 
ness; and there was time for the variations toward 
narrowness to develop and survive, ‘‘leading to a 
change in the proportions of these crabs, which, if 
continued at anything like the same rate even for a 


140 EVOLUTION FOR JOHN DOE 


century, would so alter the shape of these animals as 
to produce what would certainly be described as a new 
species. . . . There seems little doubt that we have 
here a means of seeing natural selection actually at 
work,”’ 

Natural selection is as impersonal as sea-water and 
climate; it has no design, no purpose; it molds 
heredity as mechanically as waves shape the rocks. It 
ean not create a species any more than waves can 
create granite, but can only pound away at the varia- 
tions that perpetually occur in every stream of germ- 
plasm. In the nutmeg tree, for example, there are 
constant variations; climate and competition pound 
away at the unfavorable ones, which are never allowed 
to propagate. If man interfered with the nuts, he 
might preserve variations of the rind that were 
slightly more pulpy, and by a long series of such 
selections, taking advantage of any sports in this 
direction, he might convert the bitter rind into sweet 
pulpy fruit—just as the bitter rind of an almond could 
be altered into a peach. Man could do this by design. 
The forces of nature select out from the rind every 
tendency to sweetness and pulpiness; any nut that has 
a slightly sweet or pulpy cover is not so well protected 
and will have less chance to reproduce itself. 

Natural selection has no power to help a plant by 
causing a favorable variation. If the crabs had not 
possessed in their germ-cells the apparatus for grow- 
ing narrower, if the nutmeg had no apparatus for 
producing a tough and bitter rind, natural selection 
could not operate. Insects could often lay their eggs 
to better advantage, but no useful variation of instinct 
happens to arise, and the females continue to blunder. 

Variation is not a matter of mere visible altera- 
tions; it occurs im all the fluids and organs and cells 
of every part of all bodies; chemical components vary, 


"STLO1 ge SUIYSIOM puB ‘Sumo, Joos JO “URTIBIOSOA B SBM ‘snINRsOJUOIg “OUO ST, “FBO 0} PRI STBUITUR 
fiSuny oy} VY} puws Yop YIM peyZo[a oouo osaA soUog oY} FBYZ JooLOF 07 JdB OLB OM SUOJ[OYS JB SUTYOOT 1o4ZVW 





‘sivok WOI[[tU Uoozy 10 U9} AVS—oOSR O[TYM 4IOYS B ATWO BYSBIGON FO spuBziqeyUL oy} FO stuog 








NATURAL SELECTION 141 


and nervous adjustments. A very important organ of 
earthworms, which normally is in two parts, may 
sometimes occur in three or four parts; an important 
duct may open anywhere from the tenth to the six- 
teenth segment. Some birds and giraffes lack a 
eall-bladder, and sheep have been found with three 
gall-bladders. Here is material—if it originated in 
chromosomes—for natural selection to work on. Such 
variability in every generation means that worms and 
giraffes and sheep can be adapted to new conditions 
of life, that if one sort of variation is rigorously re- 
moved, another is ready to prosper and increase and 
predominate in heredity. 

A peculiar and spectacular variation that seems to 
be rather common among larger animals is a big shift 
in the proportions of the jaws—the ‘‘bull-dog type’’ 
of face that sometimes appears in cattle and pigs. 
Fishermen occasionally find a ‘‘bull-dog cod’’; this 
seems poorly adapted for life on the fone! of the ocean, 
but it persists in appearing once in a while and might, 
if conditions changed, become the regular type. There 
used to be semi-wild cattle on the ranges of Argen- 
tina that had a bull-dog type of head—the lower jaw 
protruding, the upper lip receding, and the incisor 
teeth exposed. These are hardy enough ordinarily 
and are a favorite breed; but in a dry year, when the 
erass is short, they can not crop so close and would 
starve if man did not feed them. All about them, in 
that last inch of grass which their short upper lip 
can not get hold of, there are tons of good food, but 
they are powerless 46 pull it into fhe mouths. The 
bull-dog type seems to be continually seeking its 
chance in many parts of the animal kingdom, but is 
always removed by natural selection. It is an inter- 
esting example of the wealth of variation that selection 
has to work on. 


142 EVOLUTION FOR JOHN DOK 


Such a case shows that germ-cells are as ready to 
continue making one type as another. Professor Mor- 
gan found in his abnormal, unfit fruit-flies that 
‘‘adaptive characters are inherited in exactly the same 
way as are those that are not adaptive.’? So varia- 
tion is forever furnishing the material of adaptation, 
and heredity is always prepared to preserve it; the 
result is determined by the way in which the strug- 
gle for existence destroys forms or allows them to 
develop. 

Canaries were for untold centuries a green bird. 
For some reason the occasional yellow sports could 
not succeed—perhaps because they were more easily 
seen by their enemies. After canaries had been bred 
in captivity for two hundred years, they were still 
ereen birds. But then a sport to yellow was fancied 
by one breeder, and this became fashionable. Never- 
theless, after the green color had been ruled out by 
artificial selection, heredity could still be counted on 
to furnish occasional green birds. It acts the same 
way in nature. When rats or dogs or rabbits or cattle 
are turned out in new surroundings to run wild, the 
operation of natural selection is always seen. ‘‘It has 
happened on two or three occasions that European 
rats have been accidentally imported by ships upon 
some of these islands, and even already it is observed 
that their descendants have undergone a slight change 
of appearance, so as to constitute them what natural- 
ists call local varieties.’’* We can not guess at the 
obscure ways in which natural selection acts on such 
immigrants—why in the new surroundings a slight 
variation that used to be favorable and predominant 
is now unfavorable and perishes. But so it always is. 
‘When an animal has to struggle under circumstances 
inconcelvably complex,’’ says Darwin, ‘‘modifications 


*@G. J. Romanes, Darwin and after Darwin. 


NATURAL SELECTION 148 


of the most varied nature in the internal organs as 
well as in the external characters, will be rigorously 
tested, will be preserved or rejected.”’ 

In Europe a certain species of lady-beetle shows 
many variations of coloring, but for some reason these 
are selected out much more rigorously in America, 
and the color pattern remains very constant.* Another 
species has a much more constant pattern in the West 
than in the eastern states. A third species shows 
changeable stripes in the East and constant ones in 
the West. For reasons quite beyond our ken natural 
selection bears harder on a variation in one region 
than in another. 

These minute studies of spots on small insects may 
seem petty business, but there is as much meaning in 
those varying colors as in the prodigy of an ancon 
sheep. Colors may be matters of life and death to 
animals, and any differences in them are the result of 
severe and accurate selection in the competition for 
life. What is more, every spot of color was provided 
for in the pattern that a chromosome inherited and 
then transmitted. Here we can see how nature sifts 
out some variations and permits others to reproduce, 
though we have no clue to the reason. 

But sometimes we can understand the action of 
natural selection. One kind of animalcule,t living in 
all the oceans of the world, gives a beautiful exhibi- 
tion, as clear as any chart, of how the changes in germ- 
cells are sorted out. It is shaped like an anchor. 
From its lumpish body branch the slender, tapering 
stem and two slender, flexible arms. These arms are 
floats to support the animal at the right depth in the 
water. It will need longer floats if the water is less 


*R. H. Johnson, Carnegie Publication 122, Determinate Evolution 
in the Color Pattern of the Lady-beetles. 


+A genus of the Peridinex, Ceratium. 


144 EVOLUTION FOR JOHN DOH 


buoyant, just as a person needs a larger life-preserver 
in a fresh- WeMes lake than in the heavy water of the 












Animaleules that show 
how their floating appa- 
tatus has been the result 
of natural selection. A 
is from light water, 
where more buoyancy is 
needed; B is from heav- 
jer water.—From Weis- 
mann after Chun. 


Great Salt Lake. Hence we 
could predict that if one of 
the animals is born with 
arms too short for light 
water or too long for heavy 
water, it will be floated at 
the wrong depth and will 
perish, leaving no descend- 
ants. Investigation shows 
that this is exactly what 
happens. In the Gulf of 
Guinea, where the water is 
light because of its warmth 
and its small amount of 
salt, this creature’s horns 
have to be ten times as 
long as its body. But just 
in proportion as the water 
grows colder and _ saltier, 
so that it is more buoyant, 
shorter horns are needed. 
In one of the ocean cur- 
rents the same size of body 
is floated by horns only 
one-tenth as long as are 
needed in the Gulf of 
Guinea. Salt and tempera- 
ture do not manufacture 
horns. But they do most 
accurately select out and 
destroy all those animal- 
cules that vary in a slight 
degree from the propor- 


NATURAL SELECTION 145 


tions that are needed in any given part of the ocean. 

The longer a naturalist studies, the more he sees 
natural selection everywhere and always at work. He 
learns to decipher the stories of adaptation as if they 
were written in a book. But the language is a foreign 
one which he has to learn to translate. When he has 
become expert, the queer idioms of adaptation grow 
familiar and sensible, until at length he can make out 
a clear and consistent message of evolution. 


IV. How Natural Selection ‘‘Makes’’ Adaptations 


I will give a few common and brief examples of 
how the nineteenth-century naturalists learned to read 
the record of nature and to find out how adaptations 
were ‘‘made.’’? This knowledge has been so much ex- 
tended in the twentieth century that science now con- 
structs the histories of species almost as confidently 
as if it were telling of Rome and Thebes. 

There is a species of nut-jay which ranges from 
the Alps to Siberia. In the Alps it has to get food by 
breaking up pine-cones, and there it has a thick bill 
that is well adapted for such hammering. But in Si- 
beria it can not secure food that way; it has to reach 
into cedar cones, where the seed lies deeper than in 
the pine; and in Siberia it has a bill adapted for reach- 
ing—longer, more slender, with the upper jaws pro- 
truding a tenth of an inch over the lower. The history 
is easy to read if one knows the language of chromo- 
somes. When the species originated, those birds in a 
pine forest that varied toward slender bills could not 
live through a hard winter when the competition for 
food was keen; and in a cedar forest those that varied 
toward stubby bills could not survive a hard season 
when there was not food enough for all. In this strug- 
gle with cones and cold the unfavorable variations 


146 EVOLUTION FOR JOHN DOE 


were selected out; and as the centuries went by these 
two impersonal forces were the cause of adaptations." 

There is a genus of butterflies, widely distributed 
over the earth, that offers a puzzle in colors: in some 
species both males and females are brown; in others 
the males are bright blue, while the females are 
brown; in some species the males show only a trace 
of blue. This genus used to be as much a mystery as 
Aztee inscriptions; nobody could read its history in 
the blue and brown wings. But the record is easily 
deciphered when we use the key of sexual characters: 
the scent-scales and the blue color are male variations 
—like the spurs and plumes of birds. Those species 
that have neither character must be the oldest, and 
those in which the males show a slight color must be 
of more recent origin. If the males are bright blue 
and have well developed scent-scales, they must be 
more recent still, for variations never go backward 
along the same track. Younger still must be any spe- 
cies in which some females show a trace of blue, for 
this sex-character begins in males and goes from them 
to the females. The spread of blue shows the com- 
parative youth of a species. We should expect that 
as time went on a species would develop in which all 
the females would be a full bright blue. And this is the 
ease. In the tropics, where selection seems to work 
faster, one species has already gone to that limit. It 
must be very young—as time goes for the biologist. 
The student of butterflies is as sure of this as a his- 
torian who states that Alexander the Great occupied 
Egypt before he invaded India. 

All through the animal kingdom enemies have se- 
lected variations in the most remarkable ways. If a 
little bird is colored like its surroundings, the hawks 


*This and the two following examples are from Weismann’s The 
Hvolution Theory. 


NATURAL SELECTION 147 


soaring far above are less likely to see it; it therefore 
has a better chance to survive. But if it is conspicu- 
ous, it is likely to perish and leave no descendants. It 
is for this reason that, as a rule, white birds can not 
survive among green trees and that white pigeons are 
more preyed upon than colored ones and that dark- 
colored birds can not survive in arctic snow; experi- 
ments prove that if insects and birds are put among 
foliage to which their color is not adapted, they are 
quickly killed off. And this has always been true in 
nature. If germ-cells of insects happen to vary in 
such a way that they make a color pattern which is 
more conspicuous in the surrounding foliage, they 
doom the insect to death; if they happen to vary a 
little toward a concealing pattern, they make an insect 
more fit for the struggle, more likely to survive. As 
the centuries go by, those unfavorable habits of chro- 
mosomes are continually being sifted out; every fav- 
orable tendency is more likely to be inherited. In this 
way the birds, by killing insects that have unfavorable 
variations, gradually bring about the most extraordi- 
nary alterations of the colors of insects, until the pat- 
terns of the wings and bodies imitate the appearance 
of the leaves or bark upon which they live. 

If a certain fly succeeds better in having its eggs 
hatch because a variation has made it look a little bit 
more like the bees in whose cells it lays the eggs, 
its fortunate variation will have a chance to reappear 
in some of its offspring, and thus they will be more 
likely to prosper. Such a variation tends to continue 
and to increase. Those flies in the third generation 
that have more favorable bristles or shape of body 
will have success; and so the spurts of variation 
are slowly directed in a course that may finally 
lead to the most incredible resemblances. If chromo- 
somes shape a duckling that is somewhat better 


148 EVOLUTION FOR JOHN DOE 


camouflaged than its fellows, it is more likely to 
survive and continue a stream of germ-plasm that has 
possibilities of varying still more toward useful colors. 
If a non-poisonous snake happens to be born with 
color spots that give it even the slightest resemblance 
to a venomous species, it has a somewhat better chance 
to survive and to set going a series of variations that 
approach more and more nearly to the venomous ap- 
pearance. Its enemies are constantly allowing the 
favorable spots to survive and thus in time may bring 
about a case of mimicry that seems too strange to be 
true. But the imitation is a fact in Brazil; the evi- 
dence is so clear that.experts are forced to accept it. 

It is hard to believe that a bee’s sting was gradu- 
ally built up by a series of selections of ‘‘accidents,’’ 
and the development of such an instrument as a 
hawk’s eye is a process that makes the imagination 
blink. Certainly we should like to have some one dis- 
cover an easier theory than natural selection. 

But all the present signs are that natural selection 
has come to stay.* It is approached in so many ways, 
it can explain so many conditions, it is so in accord 
with the plain facts, that it grows in force every year. 
It has shown two generations of naturalists how the 
plants and animals became what they are. It can 
sometimes be seen at work; and whenever we assume 
that it has been at work, we secure a sensible result. 
The man who has used natural selection for many 
years does not feel that it is in the least weird. What 
staggers his imagination is to try to think how he 
could live without it. 

One illustration among the caterpillars will show 
how the practical naturalist finds that the theory will 
lead him right. The caterpillar of the death’s-head 


*The evidence for this statement is giver at some length in Chapter 
XXIV, Section LV. 


NATURAL SELECTION 149 


moth is colored in such a way that it is conspicuous on 
potato plants in Europe; it has to protect itself by 
eating at night and burying itself in the ground dur- 
ing the day. This appears to be a case where selection 
has not adapted an animal to its surroundings. But 
the caterpillar is not a native of Europe. In its origi- 
nal home, Africa, its color is a most elaborate ‘‘imita- 
tion’? of the leaves of the plant on which it feeds. 
There it stays out on the leaves all day long. 

To tell all about adaptations in animals would be 
to describe the whole animal kingdom. To give a 
slight outline would require a book. (Wallace’s Nat- 
ural Selection is a readable one.) Here we can glance 
at only a few points of the panorama of adaptations. 
The most useful will be some examples of how often 
a long series of adaptations, graded from a crude be- 
ginning to a finished product, are spread before our 
eyes in the world about us. 

If I take up a lobster’s claw* and ask myself how 
it was developed by selecting chance variations, I am 
utterly at a loss. Yet a student of sea life has seen 
the series of steps. He can take out of the ocean spec- 
imens of a dozen different species and set them in a 
row on his table to show the following graded series: 
(1) a leg, the last joint of which can bend against the 
next joint and clasp an object there; (2) some rough- 
ening of the last joint, so that the object is held more 
securely; (3) a protruding of that next joint, till it 
forms a better surface for the last joint to work 
against; (4) an enlarging and curving of the last 
joint; (9-12) further steps of the same sort to a real 
claw. The student does not have to depend on a the- 
ory; for the principal steps, the ones that are hardest 
to believe, are before his eyes. In a similar way, and 


*This and the three following examples of development are from 
the Origin of Species, and Huxley’s On the Study of Zoology. 


150. EVOLUTION FOR JOHN DOR 


with no exercise of fancy, the student of anatomy cau 
go a great deal further, can trace back from the de- 
veloped leg to a mere jointed ring of the body; he can 
look further back, down the vista of development, see- 
ing the complicated parts grow simpler, until the lob- 
ster looks almost like a jointed worm. 

Does it sound fanciful? Huxley once said to an 
audience, after he had outlined this course of develop- 
ment, ‘‘I imagine I hear the question, How is all this 
to be tested?’’? He declared to them that there was a 
time when ‘‘endless dreams about the development of 
structure threatened to supplant science,’’ and he had 
to prove to his classes that what he told them about 
the evolution of the lobster was not imagination. He 
began his proof by saying, ‘‘Our lobster was once an 
egg.’’ He described the development of this, telling 
of ‘‘the rings that are first sketched out,’’ ‘‘the bud- 
like prominences on them,’’ ‘‘the growth of these into 
appendages’’—in short, the living proof, in an em- 
bryo, of the anatomist’s theory. ‘‘These,’’ he said, 
‘fare wonderful truths—the more so because the zoolo- 
gist finds them of universal application.’? Some 
description of them is given in Chapter XVII. They 
are the sort of confirmation that no biologist can re- 
sist to-day. 

In the whole development of the lobster there is 
no sudden miracle, no alteration which does not come 
by slight changes that seem easy to account for. In 
all the elaborate machinery of legs and claws there 
is little that is really new, for most of it has been made 
by merely altering the proportions. In the case of 
animals it has been estimated that ninety-five per 
cent.* of all the evolution is nothing but the extension 
of some parts and the reducing of others. The contin- 
ued altering of the proportions of the parts of an 


*H. F. Osborn, The Origin and Evolution of Life. 


NATURAL SELECTION 151 


animal may result in a creature that appears utterly 
different. The same is true of the altering of parts 
of simple plants to produce the higher ones. It is the 
series of gradual changes of proportions that drive a 
botanist to rely on evolution. He can in most parts 
of the vegetable kingdom arrange a set of plants, 
graded by slight differences from each other, that 
lead up to the same steps by which he had reasoned 
that natural selection might have developed the plant 
that he is studying. If he has asked himself how an 
iris camé by its very peculiar apparatus of pistils 
and stamens, and if by his knowledge of how insects 
fertilize flowers he figures out the probable steps of 
adaptation, he can gather a set of blossoms that will 
parallel his reasoning. You recall Darwin’s descrip- 
tion of the orchid that gave bees a ducking in order 
to get itself fertilized, and you are skeptical as to 
how any process of selection could build such a tricky 
bath-tub; but from the seven thousand species of 
orchids a series could be arranged that would be al- 
most like a moving picture of the gradual develop- 
ment. When a botanist has compared for forty years, 
in many countries, the slight degrees of adaptation 
that fit the different species of orchids to slightly 
different insects, he believes in evolution as firmly 
as a traveler believes in railroad trains. A savage 
can not believe that steam will drive an engine, and 
he will argue the matter; but the civilized man buys 
a ticket, confident of being hauled to his destination. 
So the scientist no longer debates evolution; he uses 
it. He may have some wrong ideas about how it op- 
erates, but he knows that it works. 

The road-bed of belief in evolution is the gradu- 
ated serves of forms. An adaptation does not stand 
by itself as an isolated marvel, but is in a series of 
rather similar adaptations, a series that carries a 


152 EVOLUTION FOR JOHN DOH 


zoologist easily to his conclusion. Perhaps the ants 
come nearest to being unlike anything else in the 
world; it might seem that here at least we could not 
explain the peculiar arrangements by any process of 
selection of variations. Think of their three kinds— 
the queen, the male drones and the neuter workers. 
Yet a zoologist, familiar with a thousand kinds of 
variations of sex in all parts of the animal kingdom, 
could arrange a list of sex-adaptations that would 
represent the course of development in ants. There 
is nothing exceptional about these sex-groups. Nor 
is each sex-group made up of invariable creatures that 
are all of a kind. ‘‘The neuters of these British ants,’’ 
says Darwin, ‘‘differ surprisingly from each other 
in size and in color and in their eyes; yet the extreme 
forms can be linked together by individuals taken out 
of the same nest. . . . The difference between neu- 
ters of this African ant was the same as if we were 
to see a set of workmen building a house, of whom 
many were five feet four inches high and many six- 
teen feet high; the larger workmen had heads four 
instead of three times as big as those of the smaller 
men, and jaws nearly five times as big; the jaws dif- 
fered wonderfully in shape and in the form and 
number of the teeth. . . . Yet these sizes graduate 
ansensibly into each other.’’? That is what an observer 
always finds—variations that graduate into each oth- 
er. He can see a long course of changes, which 
stretches without a gap from one form to a very dif- 
ferent form. Nature is always setting before him 
these exhibits of how variations have been selected 
and of how readily the development can be continued. 

If I think of the delicate, almost intelligent ten- 
drils of a climbing vine, I can not imagine any graded 
series of plant apparatus from the stem of an oak 
to the clasping coil of a sweet-pea, I am skeptical 


NATURAL SELECTION 153 


and ignorant. But the botanist can not think of ten- 
drils except as graduated series of development from 
other parts of a plant. He knows that in one vine 
they have developed from branches, in another from 
leaf-stems, in another from leaves. He knows many 
kinds and degrees of tendrils. He has seen, in plants 
that have no tendrils and never climb, how the young 
stems move in their growth, tending to go round and 
round in a spiral. To him the tendril of any plant is 
just one example of the selection of favorable varia- 
tions; he can think of it only as part of a graduated 
series of such adaptations. If you removed this evo- 
lutionary conception from his knowledge of plant life, 
you would paralyze his knowledge. 

All students of nature would be staggering in the 
dark if it were not for that conception. By its light 
they can read the world of life as it is and can see 
far back through the geologic ages. In its beams they 
see the variations of a four-toed animal no bigger 
than a cat, which were selected for three million years, 
till three of its toes disappeared and its size increased 
tenfold—and it was domesticated as a horse. The 
searchlight of evolution shows up the fossil history 
of an animal in Egypt whose upper lip grew larger 
through the ages, and in which the other variations 
of shape of leg and size of body were selected, until 
the result was an elephant. When we first hear such 
wonder-stories, we are skeptics, just as we were when 
we heard for the first time of X-rays or wireless. Ig- 
norance has to be skeptical. But when we are familiar 
with photographs of our own bones and receive by 
wireless a message from our own family, we forget 
the first shock of skepticism. It is so with these series 
of adaptations. Many a modern scientist spent some 
days of boyish incredulity; now the marvel has be- 
come a commonplace in his day’s work, like the in- 


154 EVOLUTION FOR JOHN DOE 


credible telephone or the utterly impossible gasoline 
engine. | 

Skepticism is removed only by familiarity. The 
sensible man will not accept mere logic, for he knows 
how often logic goes astray; nor can he accept the 
incredible because ‘‘they all say so.’’ If any reader 
asks me how a bird’s instinct for migrating was ever 
made by the gradual accumulation of variations in 
germ-cells, I give it up. So I should be at a loss if an 
Kiskimo asked me how my voice could travel over a 
wire; for I don’t know how. What I do know is that my 
voice is heard at the other end of a wire and that a 
bee’s sting is the end of a series of variations. I know 
of some steps in the series: the first fossil insects 
were very crude; there was a long course of develop- 
ment before anything like a bee appeared, and it had 
no sting; the females had a pointed organ for laying 
eggs. That is worth thinking about. In a hive of 
bees the big males have no sting, but only those neu- 
ters which are undeveloped females. Here is the hint 
which biologists followed and which showed that a 
sting is a ‘‘modified ovipositor.’? We know that 
throughout the plant and animal kingdoms there are 
series of all sorts of variations for producing poison 
—from the prickle of a nettle to the astonishing feats 
of gall-wasps; a wasp is cousin to the bee, and it 
has developed a refined chemistry for the egg-laying 
process. So here is the same ever-repeated truth: a 
long graded series of stings and a long graded series 
of poisons. A zoologist can live and work by such 
knowledge; he can breathe if he has it, but he would 
stifle amid the nightmares of nature if he had no such 
help. 

Hiven the stages in the development of an eye can 
be shown in a series of animals gathered under one 
show-case: (1) a mere spot sensitive to light, as in 


NATURAL SELECTION 155 


certain animalcules; (2) an eye-spot that is covered 
by translucent skin and that has a special nerve; 
(3) a more developed spot, in which can be seen 
above the nerve a transparent jelly-like mass that 
acts as a lens to bring more light to the nerve; 
(4) an apparatus almost as crude, but which has a 
hard transparent covering and some coloring-matter 
at the end of the nerve; the slight steps of increasing 
complexity can be continued in a long and gradual 
scale up to the complex eye of a squid, which is so 
similar in appearance to the eye of a vertebrate. 

Amuse yourself by trying to guess how a rattle- 
snake ever got its rattle. Then look in the old Cen- 
tury Dictionary, printed almost forty years ago: 
“The rattle represents the extreme of development 
of the horn or spine in which the tail of many other 
serpents ends.’’ If you read on, you will catch a 
glimpse of the character of this animal: ‘‘ Rattlesnakes 
are sluggish and inoffensive reptiles.’’ No one could 
guess from that fact why a horn developed into a 
rattle, unless he knew that a great many animals, of 
all sorts, are so constructed as to advertise their dead- 
ly or offensive equipment. When we know about ‘‘many 
other serpents,’’ and about a long series of skunks and 
nauseous butterflies that avoid fighting by advertising 
their bad qualities, then we can see the kind of varia- 
tions that natural selection has worked with to build a 
rattle at the end of a serpent’s tail. 

It is the whole range in a graduated series, from 
slight beginning to intricate last stage, that obliges 
the scientist to accept evolution for a guide. He is 
not infatuated with the principle, has not the least 
affection for it, and would shake it off to-morrow if 
he could find anything better; but until there is a 
substitute, he will use it as a compass for exploring 
the jungle of adaptations. 


156 EVOLUTION FOR JOHN DOE 


Hundreds of keen students, noted ones and shrewd, 
have for sixty years been translating the history of 
life by the light of evolution. They have made 
some errors, have not agreed on some points, are still 
in the dark about others, and have quarreled about 
many particulars. But by their combined labors they 
have made out a fairly complete account of the gen- 
eral course of life on the globe. As to the beginning 
they know nothing, and do not pretend to know any- 
thing. They can only suppose that some original 
simple form of life, something simpler than a single 
cell, varied; that cellular structure developed; that 
several cells made up a colony; that the work of the 
colony was divided among different groups of cells, 
some securing food, some distributing it, some keep- 
ing off enemies, and some reproducing; that such 
groups varied continually in the direction of special- 
izing, and thus became adapted to live as parts and 
not as independent wholes; that the whole groups 
became bodies, with organs to see and smell and move 
and reproduce. Here were species large and distinct 
enough to be preserved as fossils; from this point on, 
a part of the record is accurately preserved in the 
rocks, 

Sixty years ago this explanation was a theory; 
thirty years ago it was so plain a truth that all the 
conservative works of reference adopted it as a mat- 
ter of course; to-day the schoolboy knows that every 
form of life is descended from an earlier and less 
complicated form. 


V. ThereIs No ‘Blind Chance’’ in Natural Selection 


It is strange to think that the whole height and 
breadth of organic life was caused by variations 
in germ-cells. It is doubly strange if we speak 


NATURAL SELECTION 157 


of these variations as due to ‘‘chance.’’ For the 
common meaning of ‘‘chance’’ is mere luck, mere hap- 
pen-so, without any particular cause. If I throw a 
quarter high in the air, making it twirl rapidly, there 
is no knowing whether the fall will be heads or tails. 
We say that there is an ‘‘even chance,’’ and we never 
think of any cause for its falling either way up. If 
‘‘chance variations’? were of this head-or-tail sort, 
then all the intricate adaptations of animals would 
have been produced by a lot of luck. 

If anybody says he believes that the world of life 
was made by luck, his statement sounds foolish. It 
doesn’t sound sensible to assert that all the stagger- 
ing marvels of an eye were formed by ‘‘mere chance.”’ 
A man might just as well say that the Panama Canal 
happened to be dug, or that a magneto pulled itself 
together one fine day by a set of accidents. So if 
the theory of natural selection were based on mere 
luck, it would seem foolish even to a gambler. 

In fact the word ‘‘chance’’ has sounded foolish to 
some people who are a great deal more logical than 
gamblers. John Burroughs, for example, was a high- 
ly intellectual man, an author of charming books; and 
he, though he loved and admired Darwin, was much 
offended at the idea that all adaptations were made 
by hit-or-miss. Other thoughtful men have felt that 
a doctrine of ‘‘blind chance’’ is very dreadful. And 
it would be dreadful. If Darwin had meant to teach 
such an idea, he would have been wild and wrong- 
headed. 

But we know that he was one of the calmest and 
most careful of thinkers. Burroughs considered that 
he had a ‘‘master mind.’’ So it is inconceivable that 
he blundered in such an elementary way. How, then, 
did Burroughs misunderstand him? By not paying 
attention to Darwin’s plain emphatic explanation of 


158 EVOLUTION FOR JOHN DOE 


what is meant by ‘‘chance.’? Burroughs supposed 
that Darwin meant, as we do, unthinkingly, in common 
talk, pure luck which has no cause. 

But Darwin used the word in an entirely different 
sense, and never dreamed that any critic would fail 
to take notice of his explanation. No critic ever would 
have overlooked it if he had known the meaning that 
is given in the next paragraph. 

Darwin was using the language of science. The 
scientist knows that nothing can ever happen without 
a cause. He says that every flip of a coin is made by 
such an amount of power as will turn it over just so 
many times before it lights, and that there is no more 
luck about turning it over one hundred seventy-three 
times than there is about turning it over once. But 
we don’t know how many times the force will turn it 
over; we don’t know the cause of the heads or tails. 
The scientist says that no drop of water on a stormy 
ocean, no atom in a chromosome, can possibly be 
altered in any way except as the result of the absolute 
law of cause and effect. Though we say in every-day 
life that ‘‘I met him by chance,’’ or that ‘‘his death 
was accidental,’’ the scientist knows that the exact 
circumstances of every moment were perfectly ac- 
counted for by the preceding circumstances. It is 
impossible to know the causes, but they were there. 
All such cases, of which we can not yet know the cause, 
the scientist refers to as matters of ‘‘chance.’’? Sav- 
ages and crap-shooters and superstitious people can 
not understand this, and college men sometimes be- 
lieve that things can happen without any cause; but 
the scientist knows that we can never escape from 
law and that there always is a cause. 

Burroughs accuses Darwin of not knowing this. 
He says, ‘‘Darwin everywhere uses the word chance 
as opposed to law, or the sequence of cause and ef- 


NATURAL SELECTION 159 


fect.’? The accusation is utterly untrue. In the Or- 
gin of Species the word is clearly defined at the be- 
ginning of Chapter V: ‘‘I have sometimes spoken as if 
variations were due to chance. This, of course, is a 
wholly incorrect expression, but it serves to acknowl- 
edge plainly our ignorance of the cause of each par- 
ticular variation.’? That is exactly his use of the 
word—to mean that we know nothing of the causes. 
He is everywhere careful to indicate that any varia- 
tion must have a cause, using such expressions as 
‘‘the dimly understood laws of variation . . . vari- 
ability is governed by many unknown laws .. . 
all these causes of change . . . variations, from 
whatever cause proceeding . . . as we do not see 
the cause, we invent laws! [said ironically] . . . dif- 
ferences given by nature; I mean by ‘nature’ only the 
action of many natural laws.’’ 

Darwin seldom uses the word chance—for fear of 
the heedless critics. Once he says, ‘‘Mere chance, as 
we may call it.’? He found it convenient and proper 
to use the short word chance as an acknowledgment 
of ignorance, instead of explaining himself at length 
every few pages. 

In another book Darwin illustrates his meaning by 
the pieces of stone at the base of a cliff: we speak of 
their various shapes as ‘‘accidental,’’ though we know 
that every least fracture was made in strict accord- 
ance with law. From these stones to the remotest 
nebula in the heavens every shape in the universe has 
been produced by definite causes. Nothing happens 
without a cause. And it is so in plants and animals. 
The infinite variety of forms was produced by strict- 
est law; for every item of structure in every individ- 
ual there is a cause. When biology tries to trace the 
causes, it can take a certain number of steps—back to 
chromosomes or genes. Farther it has not been able 
to go. 


160 EVOLUTION FOR JOHN DOE 


Science observes certain facts about the failure 
and survival of animals in their efforts to live, and it 
gives a name to those conditions. That name—‘‘nat- 
ural selection’’—is not a power that works like a 
spirit or a man. It is not a creative force. It is a 
label that is put on a great body of knowledge, just 
as ‘‘the weather’’ is a convenient name for all those 
facts of temperature and water vapor and sun-spot 
electrons that cause sunny days and cyclones and 
snow drifts and fog and rain. The weather is a set 
of forces that we feel and see. Natural selection is 
a set of forces which determine that adapted plants 
and animals shall succeed in the struggle for exist- 
ence. 


VI. What Evolution Can Not Do 


Evolution can not originate life. Children always 
inquire about first causes, expecting parents to tell 
them who made God. In much the same way we older 
people are prone to ask of evolution, ‘‘How did life 
begin??? And some scientists have speculated about 
the origin—whether the first cell traveled to us on a 
meteor, whether the first speck of protoplasm was 
made by a lucky aggregation of molecules in warm 
mud, etc. These are sheer guesses, scientific play. No- 
body has the least knowledge of how life began. The 
evolution theory makes no pretense of explaining ori- 
gins. ‘‘Biologists,’? says Woodruff, ‘‘are at the 
present time absolutely unable, and probably will be 
for all time unable, to obtain empirical evidence on 
any of the crucial questions relating to the origin of 
life on the earth.’’* 

The idea that science is trying to reach origins 
makes some people dread it. They have an uneasy 
fear that perhaps it will remove the mysteries of life, 


*Hvolution of the Harth, page 107. 


‘QAN}[NA B YL wostieduios UL UMOYS ST ozIs osoyaM ‘([AJOBpoie}g vB) sopydat pacutM ore, JO spulry AUB dy} JO 9UO 











One of the two known specimens of the earliest kind of bird that has yet been 
discovered—Archaeopteryx. It might have been called a reptile if some of its 
feathers had not been preserved. 


NATURAL SELECTION 161 


will strip it bare of sentiment, and will reduce poetry 
and religion to a skeleton of facts. Any such uneasi- 
ness is a quaint misconception. Science has no such 
expectation. The deeper it investigates, the more it 
is involved in mystery; and it does not reach any ex- 
planation of the origin or nature of life. The true 
scientist is aware of the poverty of his little store 
of facts, for he knows much better than we how awe- 
some and impenetrable are the ultimate secrets of 
the working of evolution. Huxley said that ‘‘in ulti- 
mate analysis everything is incomprehensible.’’ 

It does not cause progress. We all have a habit 
of thinking that evolution is an ascending scale of 
life, from a bottom somewhere in the slime up to a 
splendid horse or a noble dog. We have all our lives 
been accustomed to thinking of animals as ‘‘low’’ or 
‘‘high’’ in the scale, and we naturally suppose that 
a development from bottom to top means moving on- 
ward and upward. 

Mere science can detect only one case of what 
might be called progress—the advance from simpler 
forms to more complex ones. [Even to this general 
course of evolution there are big exceptions: some 
species grow simpler in form after taking up the life 
of a parasite, and a great number of simple forms of 
life seem to have persisted through the whole of geo- 
logic times without progressing in complexity. 

Otherwise science can not assert anything about 
progress. People reason about it and form opinions, 
but they can not agree on a definition of it. Science 
has not yet discovered any definition. Science sim- 
ply tells us that the forms of life are constantly alter- 
ing to adapt themselves to conditions, and it uses the 
words ‘‘better,’’? ‘‘more fit,’’ ‘‘improved.’’ But it 
always refers to temporary adjustments in particular 
cases. It can never prove that any adaptation is 


162 EVOLUTION FOR JOHN DOLE 


‘‘nrogressive,’’ but only that it is ‘‘another one.’’ If 
a simple animal is well adjusted to its conditions, it 
might be said to have ‘‘progressed’’ farther than a 
complex organism that is failing to adjust itself; but 
that is a very doubtful proposition. ‘‘Progress’’ 1s 
a matter of emotion, like ‘‘love’’ or ‘‘patriotism’’; 
and it is much less definable, and much more a mat- 
ter of prejudice. With such debatable sentiments 
science can not deal. It puts the facts before us and 
leaves us free to thrash out our opinions. Ifa scientist 
wants ideas about the one increasing purpose that 
runs through the ages, he turns to poetry and religion. 

It does not cause perfection. If we look back 
through the history of life, we find no examples of 
anything like perfection, or of any moving forward to 
it. The most admirable adaptation is only a tempo- 
rary device, dependent on other temporary adjust- 
ments. When a reptile has so altered as to live in 
trees and to fly with feathered wings, it may appear 
‘“improved,’’ and we perhaps expect a continued im- 
provement in beauty and intelligence. But thousands 
of species of birds have perished—one of the most nu- 
merous and successful and beautiful was snuffed out 
during our lifetime. Its powers of flight and repro- 
duction were no nearer to perfection than the highly 
successful reptile from which it descended. Its new 
powers meant new enemies, new perils; and no future 
adaptation of other birds will be permanent. Every 
adaptation of every animal is a way of succeeding 
fairly well, only well enough to keep the species alive 
for some thousands or millions of years, till condi- 
tions change and fresh variations are selected. 

Science tells us to use our best judgment and not 
to fight about ‘‘progress toward perfection’’ until we 
are sure we know what we mean by those words. 


NATURAL SELECTION 163 


VII. Natural Selection Begins with Variations 


‘‘Several writers,’’ said Darwin in the last edi- 
tion of his Origin of Species, ‘‘have misapprehended 
the term Natural Selection.’’ At the close of this 
Part One, we should dwell upon his words. Darwin 
had defined his term with scrupulous care, and yet 
writers had misunderstood—not pupils in school nor 
business men nor hurrying editors, but professional 
critics of a scientific theory. No reader of this ele- 
mentary chapter of a small book should be too confi- 
dent that he will keep out of error. 

For some reason even trained minds are likely to 
slip away from the one central and necessary fact. 
There seems to be some fatality in the central idea, 
for it always tends to slew around to one side and to 
hide itself. It played before the minds of men century 
after century and let them touch it; but it always 
slipped from their grasp. It played with Darwin, who 
groped for it and grabbed at it, and almost had it, and 
lost it. At length it grew over-confident. One day 
Darwin’s mind made a lucky elutch and seized it 
firmly. He describes the affair thus in his Autobi- 
ography: **I can remember the very spot on the road, 
whilst I was in my carriage, when to my joy the solu- 
tion occurred to me.”’ 

The trouble with all men up to that moment had 
been that they looked in the wrong direction. Dar- 
win directed them to ‘‘modified offspring.’’ An ex- 
planation of evolution must always begin with ‘‘modi- 
fied’’—that is, stated in modern terms, with variations 
that occur in germ-cells. We must look first at chro- 
mosomes. 

The prime fact is that chromosomes are variable. 
The ‘‘chance’’ variations in them produce offspring 
that are not exactly like the parents. These varia- 


164 HVOLUTION FOR JOHN DOE 


tions are quickly sifted out and perish if they are 
unfavorable in the struggle for existence. But if they 
make an animal more fit—even in the very slightest 
degree—they are less likely to pass through the sieve, 
and so may survive. When they survive, there is a 
slight change in the adjustment to life conditions. 
And when the change becomes great enough for us 
to see, it is called an adaptation. That is the first— 
and the last—word in evolution. 


PART TWO 


THe EKEvipences oF KvoLutTIon 


7) 
ae 
a 


yi 
eA 
at ra 





CHAPTER X 
WHAT ‘‘EVIDENCES’’ ARB 


AN ASTRONOMER can prove absolutely to any one 
trained in mathematics that the planet Venus revolves 
between the earth and the sun, but it is doubtful 
whether any biologist will ever be able to give any 
similar proof of the theory of evolution. The biolo- 
gist is convinced by numerous probabilities, each of 
which is strong, and all of which combined he finds 
irresistible. It is impossible for him to see how all 
the lines of evidence could draw together so perfectly 
toward one conclusion that is false. He would not 
be fully persuaded by any one indication, and might 
not be by any two; he is completely convinced by 
seven kinds which, quite independently, point to one 
central theory. It is the purpose of Chapters XII to 
XVIII to describe briefly these seven converging 
lines of evidence. 

The nature of these probabilities may be illus- 
trated from the study of history. Suppose that some 
skeptical reasoner should challenge the belief in the 
existence of King Alfred. Jf he had any skill and 
sense of humor, he could make a strong argument to 
show that Alfred is a mere ‘‘guess”’ of the historians; 
for the proofs that such a man actually wore a crown 
and built ships in Britain could be made to appear a 
flimsy thread—just a few old manuscripts, most of 
them written long after Alfred is said to have died. 
The ridicule could be easily made by any clownish 
essay writer. ‘T'o prove that we have reliable knowl- 
edge of Alfred would be a long task; and when the 


167 


168 EVOLUTION FOR JOHN DOE 


proof had been carefully built up, it could be laughed 
at once more as a string of ‘‘euesses.’’ In like man- 
ner the history of the rocks may seem to an amateur 
a slight and tricky record, but the geologists who 
spend their lives with it are as sure of their knowledge 
as they are of the street on which they live. 

Only the professional scholar can judge the evi- 
dences of chronicles or rocks. You and I would 
never give heed to a critic who tried to demolish his- 
tory—so long as all historians agree against him. You 
and I pay no attention to a critic who rails against 
the germ theory of disease—so long as all bacteriolo- 
sists agree against him. We do not believe in perpetual 
motion or the flatness of the earth or the effect of the 
moon on crops—so long as the whole body of special- 
ists in the subject are agreed against such beliefs. 

What is true of all lines of science holds for the 
Hivolution Theory. If we could find that many 
reputable zoologists or botanists doubted the theory, 
we might suspend judgment or might disbelieve. If 
practically the whole body of scholars is united, we 
accept what they say. We must do so if we are nor- 
mal and rational. And there is such unanimity among 
naturalists and laboratory workers to-day. To be 
sure, they have variant views as to just how the proc- 
ess has gone on; but they are all at one in believing 
that, as a matter of fact, by whatever mode, evolution 
has operated and that every present form of life de- 
veloped from some previous and different form. 

Hence Chapters XII to XVIII will be misunder- 
stood if they are read as arguments. They are de- 
scriptions of the way the whole body of scientists look 
at nature. And the chapters will be misunderstood if 
they are read as attempts to prove anything, for 
proofs are far beyond my amateur powers or ambi- 
tion. I prove nothing. I describe a great body of 
unanimous scientific conviction. 


CHAPTER XI 
THE EVIDENCE FROM THE RIVALRY OF SCIENTISTS 


Berore I present the seven lines of evidence, I 
should like to draw a picture of what scientific rivalry 
is. Though I have never seen any book that makes a 
point of this rivalry, it appears to me to be a kind of 
evidence that is more weighty for us amateurs than 
all the others. 

It is often implied that scientists are leagued to- 
gether in a kind of close corporation, that they have 
pooled their common interest and reputation, and that 
they are bound, as a kind of brotherhood, to uphold 
one another. This is a common form of superstition 
about leading bodies of men. I have, for instance, 
heard it seriously argued by a college graduate that 
‘‘the Rockefeller money power put over the Prohibi- 
tion Amendment and foisted it upon the American 
people.’’ We often hear of ‘‘the politicians’’ or ‘‘the 
judges’’ or ‘‘the clergymen’’ or ‘‘Wall Street’’ as if 
they were well-drilled armies of men who acted by a 
concerted impulse against all comers and who would 
uphold one another at all costs and without reference 
to their individual opinions or ambitions. 

However true this may be of some bodies of people, 
it has no semblance of truth when applied to scien- 
tists. Science has always been such a free-for-all 
arena that it has suffered by its dissensions. Every 
scientist is personally ambitious; he knows the short- 
comings of other scientists; he is merciless in exposing 

169 


170 EVOLUTION FOR JOHN DOE 


their errors; and he knows that if he himself pub- 
lishes an error, it will be held up to scorn by keen 
critics. He dreads nothing so much as to make a mis- 
take in judgment. He desires nothing so much as to 
make and publish a true observation that can not be 
successfully attacked. He must be perpetually alert, 
suspicious of false surmise, wary of every attractive 
novelty, diligent to avoid errors, keen to scent out 
where truth lies. If he is shrewd, he gains reputation 
and esteem. Nearly every scientist is poor; if he can 
publish a criticism that shows up some experimenter’s 
error, he may gain fame, and perhaps money. If his 
own error is shown up, he may lose what is dearer 
than either money or fame—his self-confidence. 

As a result, science is the opposite of a disciplined 
army of opinion; it is a thrashing-machine which pit- 
ilessly beats up the wheat that is fed to it, preserving 
the grains of truth and delivering the straw and chaff 
to a stack of rubbish. Every scientist tries to avoid 
the straw-stack. 

An example of how the thrasher operates may 
be seen if we imagine the feelings of three men who 
were at Harvard when Darwin’s Origin of Species 
appeared in 1859: Louis Agassiz, his son Alexander, 
and Asa Gray. Louis Agassiz was fifty-two years old. 
In his youth he had had the advantage of the best and 
most severe Huropean training; when he was thirty- 
five, he had become the foremost authority on fishes; 
he soon after made himself the profoundest investi- 
gator of glacial activity; he was the most famous 
naturalist and the most inspiring teacher of natural 
science in America. His son Alexander was twenty- 
four years old, a brilliant young fellow, who had been 
pursuing graduate study in science for four years and 
had been appointed to the United States Coast Sur- 
vey. Asa Gray was forty-nine. He had had no regular 


RIVALRY OF SCIENTISTS 171 


academic training, yet such was his diligence and force 
of intellect that he had made himself the foremost 
botanist in America. How would three such men ap- 
praise this strange new book, with its strange new 
theory—this Origin of Species? The elder Agassiz 
was strongly prejudiced against the book by all his 
German training; yet in his lifetime he had seen, in- 
deed had helped to cause, the overturning of the whole 
science of geology, and he knew that he must exercise 
a cautious judgment. If he pronounced against the 
new theory, and if his son and Gray were for it, and 
if the scientific world should accept it within ten 
years, then his triumphant career in the van of thought 
would be ingloriously ended, and he would be subject 
to chagrin and bickering in his declining years. His 
pride would not like to make a mistake where the son 
judged correctly. His pride would not like to be 
wrong where this crude, pioneerish American was 
right. Every strongest incentive of intellectual 
rivalry drove him to caution. His wits were matched 
against other men’s wits. He was more eager to be 
right than an athlete to win a race. 

He pronounced against the Evolution Theory, and 
strove against it for the remaining fourteen years of 
his life. Asa Gray pronounced in favor of it, and 
was its stoutest champion in America. As the years 
went by, Agassiz suffered the pain of seeing himself 
with an ever-dwindling minority, composed largely of 
older men. In the last year of his life he had to make 
the tragic confession to a fellow professor that his 
judgment about evolution had been wrong.* But Gray 
had the pleasure of seeing the ever-swelling majority 
grow on his side, finally including the younger Agas- 
siz. He lived to see the Evolution Theory triumph in 





*See Science, No. 1574, article by J. 8. Kingsley, 


172 EVOLUTION FOR JOHN DOE 


the world of science, and to pity his European rival 
who had placed himself on the losing side. 

Similar pictures could be drawn of episodes in 
every science. Ask any surgeon more than seventy 
years old about the theory that all infection in wounds 
is caused by micro-organisms. He will tell you of the 
conflict of opinion when he was a young man. Physi- 
cians of the old school scoffed at the new theory, which 
had never been heard of till after our Civil War. It 
had to run a long gamut of severe attack; no young 
practitioner wanted to subscribe to it if there was any 
danger that it would be disproved later; no older man 
wanted to argue against it if there was any likelihood 
that it was going to survive the test and be generally 
accepted. Professional pride made every physician 
anxious to decide correctly. The physicians were not 
in a league to uphold an idea or to denounce it; they 
all felt the spur of individual rivalry. When the germ- 
theory of contagious diseases came along, there was a 
similar situation. If any physician announced that he 
believed little plants caused tuberculosis and if the 
theory was later disproved, the physician’s reputation 
would suffer severely. If he announced that he did 
not believe such rubbish and if the medical world soon 
afterward accepted the new theory, he would be con- 
sidered ignorant and would lose prestige. So always 
in the scientific thrashing-machine: the man who can 
avoid the teeth of error is wheat; the man who op- 
poses a new truth is chaff. It is this rivalry which 
gives us laymen assurance where the truth lies. 

Whenever the result of an investigation is re- 
ported, every scientist is on the qui vive to judge it 
correctly; if he can detect any flaw in it, be sure he 
will pick it to pieces without mercy. During the last 
sixty years numberless men have thought they saw 
flaws in the Evolution Theory, and some account of 


RIVALRY OF SCIENTISTS 173 


their attacks upon it is given in Part Three. But 
since 1890 no scientist of note has contended against 
the theory as a whole. 

Weare all apt to misunderstand the nature of argu- 
ment about scientific truth. Most of us know only the 
sort of discussion that deals with opinions on large ab- 
stract questions—for example, of politics, religion, so- 
cial problems, education. In such matters we have no 
positive demonstration, but can talk and talk; there is 
no possibility of sharply checking up by a set of facts 
and finding out whether we are right or wrong. Hence 
we seldom care to find out. Our emotions are en- 
listed. We are free to think and reason and declaim 
as long as we like. The more we reason, the more 
convinced we become that we are right. We cherish 
our opinions as a faith that is very dear to us, that 
we could not bear to lose. ‘‘The truth’’ is usually 
some mental state that 1s sacred to us and that we 
propose to defend with our lives and our sacred honor 
so long as we shall live. 

To some extent and in many cases scientists are 
infected with this same human weakness: they may at 
times develop affection for a theory, and contend for 
it with ardor, but in general ‘‘the truth”’’ is an entirely 
different matter for a scientist. Truth is for him a set 
ot facts. He would no more oppose them than he 
would butt his head against rocks; he does not love 
them; he does not engage in battle for their sake. His 
only concern is to find where the facts are and not to 
collide with them. He has no more fondness for a 
theory than he has for a poor tool when a better one 
comes to his hand. If he has lived by a certain theory 
for fifty years, believing it entirely and guiding him- 
self by it, and if to-morrow he perceives a better 
theory, he will discard the old one and take up the 
new one. 


174 EVOLUTION FOR JOHN DOE 


Here are two illustrations: (a) Ever since chem- 
istry was a science the chemists have pooh-poohed at 
the idea of the transmutation of elements; but when 
transmutation was discovered in radio-active sub- 
stances, they accepted the new truth as gladly as they 
discarded their old ignorance. (b) For nearly three 
centuries the physicists taught us that light was a set 
of waves in an invisible substance named ‘‘ether.’’ 
This was not a pure invention; it represented in a 
very useful formula all the known facts about light. It 
served science well through those centuries, and no 
one could disprove its existence, though fame awaited 
any man who could dissipate it. Did the scientists 
dote on their dear old ether and long to preserve it 
against skeptical attack? Their hearts have never 
warmed to it. Already they are preparing to throw 
it overboard, because Kinstein and Michelson are mak- 
ing its existence very doubtful. 

They are a hard-hearted lot. They would throw 
evolution overboard next year if anybody could prove 
another more feasible explanation of the forms of 
plants and animals. They are no more devoted to 
evolution than they are to traffic congestion in a city. 
The minute that any one can show them a way to 
direct the streams of facts more conveniently, they 
will give him a cheer and accept his method. Every 
one of them knows this. He would rather discover the 
new solution than be president of the United States, 
for his fame would be commemorated on bronze tab- 
lets through all succeeding centuries of scientific 
history. The prize is supreme; the contest is open to 
all; every biologist would like to pull evolution down 
from its pedestal. But no one is yet in sight who can 
do the deed. 

Such a super-scientist may arrive some day. This 
chapter is not a prophecy that evolution must 


RIVALRY OF SCIENTISTS 175 


through all future time be the ultimate truth, but only 
an explanation of how it is still ultimate after sixty- 
five years of testing, and bids fair to remain so. 

This chapter has frequently used the word 
‘‘theory,’’ and so it may seem to imply that the main 
business of science is to think up grand explanations 
of general principles. Such a notion would be the 
opposite of the truth. Most scientific work consists 
in observing and classifying facts, without any effort 
to make them conform to a theory. Hence it is unlike 
philosophy and theology and political speculation, 
where reason and logic are all-important. A scientist, 
in the last analysis, cares for nothing but facts. When 
a great mass of facts can be shown to be related as 
one general principle—for example, that every living 
organism had a parent—that principle is accepted as 
a handy device for the time being. It is temporary. 
It has no validity in itself. Scientists expect their 
theories to be altered or abandoned whenever any in- 
vestigator can push his way into a new realm of facts. 
They are serenely indifferent to the fate of theories 
if only they can learn of new facts. 

We laymen hardly know what such an attitude of 
mind is. Our habitual mental state is to believe some- 
thing vigorously and want to fight for it, or to dis- 
believe something violently and want to contend 
against it. ‘‘Evolution!’’ I once heard an old lady 
exclaim, ‘‘why, I shouldn’t believe it if I knew it was 
true!’’ She frankly confessed her state of mind, 
whereas most of us conceal it even from ourselves. 
That is the reason why most of us misconceive the 
whole way of thinking of a good scientist. We in- 
evitably regard him as one of a party—as if he were a 
Methodist or a Republican or a Socialist—a person 
who has a creed to defend. He defends nothing. His 
only purpose is to keep on the right side of the facts, 


176 EVOLUTION FOR JOHN DOE 


to decide which observation of facts is right, and not 
to be worsted in the perpetual rivalry of wits where 
he is a competitor. 

This rivalry is for the most part concerned, not 
with theories, but with small matters of fact. For 
example, a cave is discovered which contains some 
animal bones beneath a layer of gravel, and two feet 
down beneath them some human bones. Now what is 
the fact? Were the animal bones deposited in the 
cave after the human bones were covered up? If so, 
there is a chapter of prehistoric life to be read in one 
way; and the discoverer may so interpret the facts, 
and may publish his findings. Much depends upon his 
one bit of evidence. If he observes correctly, his name 
will be acclaimed in the scientific journals. But 
another scientist is suspicious. He carefully examines 
the cave to see what evidence there may be that the 
human bones were deposited artificially after the ani- 
mal bones had been laid in place by a process of 
nature. If he can prove that the first observer was 
careless, he will capture the laurels. Every investi- 
gator, in the field or in a laboratory, is subject to that 
wholesome fear of being proved careless; if he dares 
to announce a verdict, he knows that he has invited 
inspection and courted hostile criticism. All the hun- 
dreds of specialists whose patient labors are mapping 
the rocks of earth know that any error will some day 
be detected and return to plague them. Livery bac- 
teriologist who reports what he thinks he has seen 
under his microscope is keenly aware that a dozen 
rivals will check his experiments and will pounce upon 
any error. It is thus that every shred of the Evolu- 
tion Theory has been tested. It comes to us as from 
a blast furnace of hot rivalry, where false assumptions 
are purged away. | ; 

Nowhere is the rivalry more intense or useful than 


RIVALRY OF SCIENTISTS 177 


in reading the bits of fossils. To me, in my ignorance, 
it is incredible that a single bone could furnish trust- 
worthy evidence. I shouldn’t know a human femur 
from the fibula of a baby dinosaur. I can’t under- 
stand how it is safe to reconstruct from one bit of 
bone a whole skull and to declare how much brain- 
power it used to house. But the rivalry among paleon- 
tologists makes it safe to credit their reports. Long 
familiarity with all the details of all sorts of skeletons 
makes scholars sensitive to small clues. So a librarian 
of experience will tell you from one quick glance at 
the outside of a book that it was published in the 
United States about 1820; an orchestra leader will tell 
which one of twenty violins is flat; a blind man learns 
to detect unmistakably the most infinitesimal differ- 
ences of sound and touch. Of course the students of 
fossils make errors, but if their competitors can find 
no flaw in a certain man’s diagnosis, we may rest as- 
sured that it is fairly safe. 

We non-scientists have small conception of how 
unremitting and exacting is the rivalry that tests out 
every announcement of a new experiment or observa- 
tion. It is the best of evidence for the Evolution The- 
Ory: 


CHAPTER XII 
THE EVIDENCE FROM THE ROCKS 


IMAGINE yourself on a Nebraska farm. The land- 
scape is a'series of gently rolling hills covered with 
rich grass, and not a rock is to be seen in any direc- 
tion for a hundred miles. Here are two knolls differ- 
ent from anything in the region, composed entirely of 
gravel and rounded stones, some a foot in diameter. 
You are a thousand miles from the ocean, and yet in 
one of these small boulders is a perfect sea-shell, such 
as was never made in fresh water. How did the stones 
and the shell reach this position? This is a trifling 
example of the unanswerable questions that curious 
minds had always been putting when they observed 
the surface of the earth before 1700. In the Rocky 
Mountains there are beds of coral; there are vast beds 
of lava where no volcano is in sight; there are sea- 
shells near the top of the Alps; embedded in the rocks, 
hundreds of feet below the surface, there are impres- 
sions of leaves that are as precise and complete as if 
they had been made last week in the finest plaster-of- 
Paris; there are tracks of all sorts of animals, as 
legible as last night’s hoof-prints to a hunter; there 
are skeletons, preserved with the minutest accuracy, 
of animals unlike anything that lives to-day. The 
frocks that bear these evidences of past life are of all 
kinds—some lying in level layers, some tilted, some 
in broken arches, some partially fused by heat. 
Inquisitive minds had wondered for twenty-five cen- 

178 





Said to be the most perfect dinosaur tracks ever discovered. They were found 

and photographed in Arizona, 1924, bv Mr. Charles L. Bernheimer, who kindly 

allows me to use one of his prints. The animal had a foot 14 incnes wide and 
took 42-inch steps. 





‘¢Tyrannosaurus rex,’’ or king of reptile tyrants, probably ruled more than 

seventy million years ago. His skeleton in the American Museum, 18 feet tall, 

was the basis for the work or the artist who advertised ‘‘The Lost World,’’ a 
sensational motion picture. 


THE EVIDENCE FROM THE ROCKS _ 179 


turies whether these old manuscripts of nature could 
ever be deciphered—written as they are in an un- 
known language on broken and jumbled leaves of rock. 

The ancient Greeks reasoned quite naturally: ‘‘If 
there are sea-shells in the mountains, then the sea 
must at one time have been where the mountains now 
are.’’ That was a very sensible supposition. It 
would have been followed up and proved bit by bit 
long before 1700 if the theologians had not been afraid 
that every such effort at explanation was an attack on 
the Bible. It was dangerous to teach that the earth 
was round, because the Bible said it was flat; it was 
impious to believe that the earth moved, because the 
Bible said it stood fast; it was blasphemy to 
guess that the hills and the ocean had changed 
places in the course of ages, because the Bible 
declared that the hills were everlasting and that 
bounds had been set for the ocean; to reason about 
the great age of mountains was atheism, because the 
Bible taught that the world was less than six thousand 
years old. Nearly all the devout people in Christen- 
dom honestly feared that any investigation of the 
earth’s surface was perilous to the spiritual welfare 
of the human race. As late as the American Revolu- 
tion there were eminent divines who denounced the 
idea that there was ever an ocean where the White 
Mountains now are. If Noah’s flood would serve to 
explain the rocks, well and good; but any reasoning 
about another flood more than six thousand years ago 
was an attack upon religion. 

All this is hard for us to realize in our day; and 
yet we still hear echoes of this dread of science. Some 
old-fashioned people are still afraid that the evidence 
from the rocks may damage the Bible. It is comical, 
though it is disheartening, to see that the human mind 
could ever have had faith in a Bible about which it 


180 EVOLUTION FOR JOHN DOK 


was so timid, or could ever have been so superstitious 
as to think that the sacred Testaments were a volume 
of science. The great majority of the men who laid 
the foundations of geology were believers in the spir- 
itual truths of the Bible and the real defenders of it; 
they insisted that it should not be desecrated by being 
dragged into the scientific arena, but that it should 
be elevated above and beyond science. It is still 
necessary to state this fact in every popular explana- 
tion of the record of the rocks, though it has long 
been a truism and will probably not have to be re- 
hearsed many years more. 

Under this fear of seeming to dispute the Bible 
every investigator labored in the eighteenth century. 
I will give only one illustration of how they were ham- 
pered, and then sketch briefly the history of the 
reading of the record in the rocks. 

I once saw some tracks in the surface of a newly 
Jaid cement road. Any man in his senses could have 
known that they were not made by an elephant or an 
ostrich or a lizard; even an ignorant fellow like me 
could know to a certainty that they were not formed 
by any animal with a hoof, nor by a rabbit, nor a 
squirrel, nor by a cat, nor by any dog less than a foot 
long. A keen trapper would have described, beyond 
any shadow of doubt, just what kind of dog made the 
tracks. If, now, I could have covered those few square 
feet of road, so that no sunshine or moisture or frost 
or chemical could disfigure the tracks, and if I could 
thus have preserved them completely for a year, 
another trapper could have known exactly what the 
first one did about the cause of the tracks; and ten 
years later, and fifty, and a hundred it would have 
been just as certain how the tracks were made. After 
a thousand years perhaps that kind of dog would be 
extinct, but a man in that age would recognize that the 


THE EVIDENCE FROM THE ROCKS 181 


tracks had been made by an animal nearly like some 
variety that he knew. After ten thousand years the 
record would be unmistakable, and after a hundred 
thousand, and after a million; those half-dozen foot- 
prints would be evidence that in some minute of by- 
gone ages some animal had set its feet in some soft 
substance that hardened and preserved the outline of 
its tracks. Hven more unmistakable are the shells and 
skeletons that have been preserved by nature in a 
similar way. Yet the men who found fossils in the 
eighteenth century were asked to believe that the shells 
and bones were not real, but were ‘‘sports of nature,’’ 
tricky likenesses—_perhaps placed there by the devil to 
lure men away from religion. It is likely that if any 
American professor had taught in 1750 that fossils 
were ancient remnants of real life, the president of 
the college would have asked him to resign. 

But by that time the collectors of Kurope had piled 
up and classified such stores of fossils that it became 
impossible for them to believe that the specimens 
were sports of nature. They had every appearance of 
being just as real as a feather or a skeleton found in 
the woods. Here and there through the centuries 
observant men had dared to speak of fossils as proofs 
that the ocean had been where mountains now are— 
for example, the great artist and scientist da Vinci 
wrote in his note-books about 1500 a lucid account of 
fossils; and an Englishman had published before 1700 
a book of similar reasoning about them. Contribu- 
tions of this sort continued all over Europe through- 
out the eighteenth century, so that by 1800 the world 
had pretty generally accepted the fact that fossils 
were made more than six thousand years ago and 
were not deposited by Noah’s flood. 

All through the eighteenth century there was also 
in all countries a diligent study of the rocks them- 


182 EVOLUTION FOR JOHN DOE 


selves. It began to be clear, as workers from 
different fields compared notes and showed up one 
another’s errors, that there had been a history of the 
earth’s surface, that rocks varied in age, and that, in 
a general way, the youngest were on top. Many 
speculations were put forward as to how rocks were 
made, how they could be heaved thousands of feet 
above the sea, and what epochs of rock-making could 
be figured out from the jumble of evidences. At the 
time of the American Revolution the generally ac- 
cepted theory was that the whole earth must once have 
been covered by the ocean, that the different sets of 
rocks were ‘‘deposited’’ by the ocean (somewhat as 
salt is when brine evaporates), and that three prin- 
cipal classes could be distinguished: the ‘‘primary,’’ 
or oldest, which showed signs of having been fused by 
heat; the ‘‘secondary,’’ or level strata on top of these; 
the ‘‘tertiary,’’ or loose sand and soil. It was taken 
for granted—as most of the population of the United 
States still suppose—that by studying the rocks men 
could find out which kind were early and which kind 
were late. It was, for example, assumed that lava was 
more recent even than the ‘‘tertiary’’ gravel, because 
men had seen it poured out on top of the soil. 

All such efforts to construct a history of the earth’s 
crust would have come to nothing. Lava flows have 
been found underneath the folded ‘‘primary’’ rocks; 
level ‘‘secondary’’ strata have been found under the 
‘‘primary.’’ There is proof that in one place lime- 
stone 1s more ancient than sandstone, and that in 
another place sandstone is more ancient than lime- 
stone. We now know that different sorts of rocks 
have been made at many periods of the earth’s 
changes. No history of them, as rocks, could ever 
have been discovered. 

The clue to the history proved to be the fossils 


THE EVIDENCE FROM THE ROCKS 183° 


embedded in the rocks. More than two centuries ago 
several Italian scholars published explanations of this 
general idea. They argued that rocks were probably 
formed in the ocean by the depositing of mud brought 
by rivers; that successive layers of this clay or sand 
or gravel were hardened into successive strata 
of rock; that certain kinds of animals were living 
when each stratum was formed and that these were 
preserved in their respective layers; and that, there- 
fore, whenever you found similar fossils in two sets 
of rocks at different parts of the earth, you had rocks 
of about the same age. We must sympathize with 
the men of that time who considered this theory fan- 
ciful. It had to stand the hardest kind of attacks for 
a hundred and fifty years, and it would not have 
survived if it had ever once been at fault. It has 
never failed to stand the test. Every decade has 
brought fresh evidence that it is the only key to the 
hieroglyphics of geology. 

Late in the eighteenth century the head of a 
French monastery occupied himself with the study of 
the shells in some limestone cliffs near the Rhone 
River, just as an Austrian monk in the next century 
studied his peas with scientific accuracy; and both 
became contributors to the Evolution Theory. The 
French abbot found five distinct sets of shells in the 
successive layers of limestone, and in the lowest layer 
were no Shells of species that then lived in the world; 
from here to the top the shells grew increasingly to 
resemble modern types. 

In 1815 an English surveyor, William Smith, who 
had for many years systematically observed fossils 
over large areas of England, published the maps in 
which he had classified the rocks according to the 
ancient plants and animals embedded in them. So 
thoroughly and shrewdly did he do his work that no 


184 EVOLUTION FOR JOHN DOE 


serious flaw was ever found in it, and it became the 
starting point of all true histories of rock that have 
been made since his day. In proportion as more and 
more old species are discovered and as wider and 
wider areas of land are explored, the truth of the 
fossil history becomes more evident. The more it is 
put to the test, the stronger it grows. A modern 
geologist could no more expect it to be overturned 
than you and I ean distrust our theory that winter 
will come again after next summer. Our faith in the 
coming seasons may be merely a theory, but we have 
confidence in it. 

Throughout the nineteenth century the classifiers 
of fossils in Europe increased in numbers and knowl- 
edge and skill. Many wrong conjectures were made, 
many errors of observation; but the rivalry of science 
was always grinding down the mistakes and preserv- 
ing the facts. Some wild theories were advanced by 
men who could not accept the crude ideas of evolution 
current before Darwin’s time. One brilliant French- 
man, for example, inferred that at many times in the 
earth’s history there had been a complete destruction 
of all plants and animals and that each time a new 
and more advanced series sprang suddenly and mirac- 
ulously into existence. His guesses were disproved. 
Irom all sides, from students of all sorts of fossils in 
the new world and the old, came an increasing mass 
of evidence that there had been only one series of life 
and that it had developed continuously. There was 
increasing evidence that no great breaks or ‘‘cata- 
clysms’’ had ever occurred in the earth’s history. 
And as the outline of the history took clearer shape, 
it was seen to stretch farther and farther back into 
remote times. In 1778, when Buffon estimated that 
all life had lasted about fifteen thousand years, he 
was considered extravagant; but fifty years later a 


THE EVIDENCE FROM THE ROCKS 185 


hundred times that many years would have been 
thought a very low limit. 

Though the knowledge of fossils continued to grow 
in fulness, it could not be assorted into any orderly 
arrangement, because scientists did not know what 
the succession of types of fossils meant. There were 
the shells and bones, as plain as any sign-board, but 
they were in a cipher code. The greatest of the early 
scholars, Cuvier, published a vast lot of information 
between 1800 and 1830: he saw that elephants unlike 
any now living had once roamed in jungles where Paris 
stands; he saw the hippopotami and rhinoceroses and 
crocodiles that used to walk in France; he studied 
countless fishes and birds and serpents that no longer 
live. But what of it? How could these signs in the 
tiers of rock be decoded? Other men found, in widely 
separated places, very precise arrangements of coiled 
shells; they were graded from the plain types at the 
bottom, through fluted and ornamented types, to a 
less ornamented type, and finally to a plain but 
noticeably different type at the top. In England and 
Italy and Germany were the same messages. They 
stared naturalists in the face, grouped as accurately 
as if they had been so many sizes of gravel-stones run 
through successive sieves; and nobody knew the mean- 
ing of this arrangement. 

Yet even Cuvier agreed that one fact was obvious: 
‘‘there has been an upward development in the animal 
forms inhabiting the globe.’’ No evidence ever ap- 
peared on the other side. As new series of fossil 
plants and animals were reported from America and 
Russia and India, they always showed the same kind 
of arrangement: from the forms in the lowest stratum 
there was always development of some sort toward 
the forms in the highest stratum. No one discovered 
any arrangement of the opposite kind, or even of a 
somewhat different order. 


186 EVOLUTION FOR JOHN DOE 


By 1840 there had been reports from many parts of 
South America, from Australia, and from parts of 
Africa; the Geological Society of London and the 
Geological Survey of New York had been established. 
Everywhere men were scrutinizing the rocks and 
fossils, recording what they saw in their part of the 
world, reading of what other men had seen in their 
countries. Murchison had gone below the coal beds 
in Wales and had found there the same kind of evi- 
dence that had been found above—that is, distinct 
layers of rock, each of which bore its own special 
assortment of fossils. He named these newly discov- 
ered formations after the ancient inhabitants of 
Wales, the ‘‘Silurian,’’ and confidently predicted that 
whenever the Americans could get a glimpse of rocks 
lower than their coal beds, they would find there the 
same Silurian fossils, in the same order. And his 
prophecy had been fulfilled. In another part of Wales 
the Reverend Adam Sedgwick, an adept in unraveling 
rock mysteries, discovered a still older formation, with 
its distinguishing kinds of fossils; and this he named, 
after the ancient Wales, ‘‘Cambrian.’’ 

By 1850 dozens more of inquisitive geologists had 
learned so many more details of these ancient records 
that they could tell the difference between the earlier 
and the later layers of each group. So intimate be- 
came their knowledge of the different shells in the 
layers that if they had received from another part of 
the world a certain sort of hinge on a shell of a cer- 
tain size, they would have known instantly whether it 
was of the Cambrian or the Silurian age; they could 
have told what other shells would be found alongside 
it, that certain other shells might be above this layer, 
but could not be below tt. 

No exception was ever found to this order of the 
fossils, Of course there were all manner of complica- 


THE EVIDENCE FROM THE ROCKS _ 187 


tions and apparent discrepancies. Many kinds of 
animal and plant remains were found almost un- 
changed through many ages of rocks, so that they 
would not serve as indexes to periods. There had to 
be wide study to learn what shells were indexes, and 
what the combinations of fossils signified. But in the 
main the fossil clues were found to be invariable and 


Q 9 po Si 
‘ 
a Palsi\ Q@ g 
was wu 'v | 3-@ OD 2 
: ‘ 
Wee: Vt Br oS eA A 
a ‘ \ =\mil, . LE 7 Pie 
‘ bs pee - bs 
a? Paid ‘i ait es tel 4 
Pi ia -_- — 
’ suick me ag J AN -< ase y. ) 
ro i re ~— 5) pe al ag ae gale an 
Codie So ‘J , Tate hi a > arin ieee 2 
‘ Nee h oy ef ~~ 
meh Ye 8) ~~ 
@___-- care Wore Se Vie ‘ 
Cet Fannie ares / 
2 ="? = 
gS ¢ . i i g 
\ \w , 
hit eee ieee ey F bi Oe 
§ Vid Wy ey N=, oa 
Vi mit se vis 7 w ¢ 
“ty SR eh cueotaa maT? nde, 
=\ WV Ps 4 
ui a) £7 ? ad 
De Weed ‘ pee 7) , 7 
NL Xy i. gr as o i 4 ie 
=? x\\ 7 rat ~<a -~gs2- = 
A = . fp 
& a’? qs 
A Ald ‘ \ ae 
SAAN ARI SN o $i agee a 
Se VERS SE MATL ASEAN Tee IC ec Lia Vie 
a \ .\ lyr \ L af Noe 
a -~.™N ‘ Pa i - * Es t 
=~ ~My 4 ¢ et ’ vA 4 ¢ 
o “> pel x SN gs we Ign = c b 
on StS 4 { % oe cso 
7! ae te he } seh ~ 
Ss ‘He 
~, 4 ‘ hb. 
Ye U4 
‘, he 
VD) 
vile 
Pe a 
aN | Pi 
ef 
Sd WA 
YV 
7 


Diagram, from Goodrich’s Living Organisms, to illus- 

trate the growth and death of species. The extinct an- 

cestors in the fossil record are shown by dotted lines; 
species still living are, shown in black. 


unfailing. The coiled ‘‘ammonite’’ shells became an 
alphabet of the earth’s history, as unmistakable as if 
they were the letters MES O2ZOZTIOC. In each 
decade since 1850 the knowledge has broadened and 
deepened, and grown in detail. If any single exception 
to the order of the fossil record had ever appeared, it 
would have blighted the whole science of geology—= 


188 EVOLUTION FOR JOHN DOB 


just as surely as the proof that there was once a king 
of the United States would upset all our school 
histories. And fame has always awaited the geologist 
who could prove such an upset of the fossil record. 
But no man has been able to discover the exception. 
A geologist no more questions the story of the rocks 
than a boy who reads about yesterday’s league base- 
ball thinks the games are a myth. 

Yet the geologists of 1859 were in the dark. By 
their flash-lights here and there they saw the unmis- 
takable record; they pieced it together; they knew it 
as surely as they knew that they had eyes, but they 
knew it as a patchwork of incomprehensible frag- 
ments. The greatest of them all during a whole 
generation, Sir Charles Lyell, had no faith that there 
was any general progression of forms from the earliest 
times to the latest. His clear-headed judgment on all 
the facts that men had piled up was simply this: ‘‘We 
have not proved any progression of forms, from sim- 
ple ones to complicated ones, through succeeding ages. 
We may yet discover the bones of a mastodon among 
the Cambrian shells.’’ 

Imagine what the Evolution Theory would have 
meant to you if you had been Sir Charles Lyell in 
1859. ‘‘If Darwin is right,’? you would have said, 
‘‘then his idea is like the glint of sunshine to a person 
who has been lost in the mazes of a cavern; if I follow 
his theory, I shall be in the daylight henceforth. But 
if it is wrong, it will be only the flicker of a candle in 
the hands of another man as lost as 1am. Is Darwin 
right or wrong?’’ That was the question that Lyell 
faced when, early in September, he unwrapped a bun- 
dle of some of the page proofs of the Origin of Species 
that had been sent by a London publisher. And 
imagine how you would have felt if you had been Dar- 
win. After twenty-five years of constant labor and 


THE EVIDENCE FROM THE ROCKS 189 


thought you have put your conclusions into the thrash- 
ing-machine. Are they wheat or chaff? Will this 
greatest student of rocks and fossils accept my theory? 
He is sixty-two years old; can he, at such an age, alter 
his whole view of the nature of life? 

‘“‘Tho not be in a hurry in committing yourself,’’ 
wrote Darwin to Lyell on September second. ‘‘Re- 
member that your verdict will probably have more 
influence than my book at present; in the future I can 
not doubt about the admittance of my views, and our 
posterity will marvel about the current belief.’’ On 
the twentieth he wrote again: ‘‘As I regard your 
verdict as far more important than that of any other 
dozen men, I am naturally very anxious about it.’’ 
On October fifteenth he wrote to Hooker, the foremost 
botanist of England: ‘‘Lyell seems staggered by the 
lengths to which I go... .. . L entertain hopes that he 
will be converted, or perverted, as he calls it.’’ On 
October twenty-third, again to Hooker: ‘‘I had not in- 
ferred from Lyell’s letters that he had come so much 
round. J remember thinking, above a year ago, that 
if ever I lived to see Lyell, yourself, and Huxley come 
round, I should feel that the subject is safe.’’ 

He had only a month to wait. Then came a note 
from Hooker which spoke of ‘‘your glorious book’’ 
which will be ‘‘very successful’’ and of how ‘‘Lyell is 
perfectly enchanted and is gloating over it.’’ Lyell 
had already determined to admit the new theory to a 
revision of his Geology, and Darwin wrote to him: 
‘‘T’o have maintained, in the position of a master, one 
side of a question for thirty years, and then delib- 
erately give it up, is a fact to which the records of 
science offer no parallel. I rejoice profoundly.’’ 
Huxley wrote a favorable review and girded on the 
whole armor of his intellect to fight the good fight for 
evolution—or, as he put it on November twenty-third, 
‘‘T am sharpening up my beak and claws.’’ 


190 EVOLUTION FOR JOHN DOE 


The whole meaning of the Evolution Theory 
to geology was thus summarized by a correspond- 
ent who wrote on the same day as Hooker: ‘‘How 
could Sir Charles Lyell, for thirty years, think 
on the subject of species and their succession, and yet 
constantly look down the wrong road!’’ Ever since 
1860 geologists have been able to look down the right 
road. Read any text-book or encyclopedia article, and 
you will find testimony similar to this from the Britan- 
mca: “‘The Origin of Species produced an extraor- 
dinary revolution in geological opinion. The older 
schools of thought rapidly died out, and evolution be- 
came the recognized creed of geologists all over the 
world.’’ In the light of the knowledge of evolution they 
have read a record of vast eras, a record which is all 
consistent, intelligible, indisputable. They could no 
more continue their researches without evolution than 
a historian could read if you took away his theory that 
lines of print begin at the left-hand side of the page. 
Hundreds of geologists are mapping rocks in all quar- 
ters of the globe. If they assume that all species of ani- 
mals developed from previous species, they can make 
sense of the fossil record; if they should assume any 
other explanation, all geology would become a heap 
of meaningless curiosities. 

No achievement of the human mind is more credit- 
able than the building up of a connected narrative of 
the changes in the earth’s crust. I offer a brief sketch 
of the result as an example of what the Evolution 
Theory produced when it was applied to this stupen- 
dous riddle and was found to be an unfailing guide. 
The first four paragraphs have nothing to do with 
evolution and do not tell of a proved theory, but I 
include them in order to furnish a beginning of the 
story. It is based on The Origin of the Earth (Uni- 
versity of Chicago Press), by Professor T, Q, 


THE EVIDENCE FROM THE ROCKS 191 


Chamberlin, a little book which is quoted with respect 
in recent scientific works. 


A billion years ago or more, as one of the stars, 
our sun, was soaring along calmly, another star came 
near. This meeting was quite in the ordinary course 
of things, for by the law of chances there must be 
now and then such encounters in the wide spaces of 
the heavens. It would appear that the star was larger 
than our sun and that its course happened to swing 
it very near the sun, though not producing a collision, 
and then to speed it away. Perhaps the meeting was 
only for a few days, or a part of a day. The bulk of 
the star almost disrupted the sun, for its attraction 
was so great that the matter of the sun began to 
stream out toward it; and if it had come a little 
nearer, it would have drawn the whole sun to itself. 
So adjusted did its course happen to be that during 
its approach it caused four bolts of sun-stuff to shoot 
forth, four more as it receded, and then sped away 
without doing more damage. (Such results are not an 
astronomer’s dream; cold figures show that just these 
effects would be produced by a meeting of a kind very 
likely to occur.) 

In such a sudden and spectacular way was the sun 
set upon and almost annihilated. Yet it had not been 
much diminished—no more than if you should draw 
off from a molten mass the size of a baseball enough 
material to make a small marble. The wreckage of 
the encounter was strewn about the sun in eight irreg- 
ular bunches of molten minerals and gases, which 
rapidly cooled, spread out as they were in a tempera- 
ture of four hundred fifty degrees below zero. They 
had darted toward the star, bending after it as it 
raced away, but it had been too fast for them. So they 
were left within the range of the sun’s attraction, yet 


192 EVOLUTION FOR JOHN DOE 


unable to return to their warm home. ‘There was 
nothing they could do but continue to whirl in orbits 
around the sun. And there they have whirled ever 
since—eight planets, of which the third from the sun 
is our earth. 

Hach of these shapeless baby planets began to set 
itself in order. Its core rounded into a globe, to which - 
the outlying fragments were attracted. As it went 
along its orbit, it was continually drawing to itself the 
wreckage that lay there. As the centuries went by it 
continued to mop up its path, to gather the debris to 
itself, and so to increase in size. Countless tiny plan- 
ets, the ‘‘planetesimals,’’ pursuing their private 
courses around the sun, were daily drawn into the 
major planets. 

That is the picture that the ‘‘Planetesimal Hy- 
pothesis’’ offers us of the origin of the earth. It isa 
conjecture so carefully calculated that it seems highly 
probable. According to this theory there was a period 
early in the earth’s infancy when it was not half so 
large as now, cooled from its original heat, already 
surrounded by some air, and having on its surface the 
beginnings of an ocean. It grew gradually and uni- 
formly, as cool at the surface as it is now, by picking 
up the bits of sun-stuff that it encountered. Since 
that earliest and briefest period of infancy it has 
never been molten, never even hot on the surface, 
never the scene of violent changes, never more dis- 
turbed by volcanos and earthquakes than it is at pres- 
ent. The history of our earth has been a placid one. 

‘‘Gradually, calmly, uniformly’? is what the his- 
tory of the rocks is forever repeating to us. Most of 
us have been familiar with the contrary idea. ‘‘There 
were tremendous doings here once,’’? I have heard 
passengers remark as they look at the Rocky Moun- 
tains from a train; they think of the past as a violent 





The Diatryma, from Wyoming, has to be called a bird, though it was unlike 
any ancient or modern bird and conld not flv. ' was a queer, unsuccessful twig 
of the tree of life. 


STAGE 7 
UPPER GHADRON 


STAGE § 
LOWER CHADRON 


sea 


ND RIVER |e CG IDGER 


ses 





These rhinoceros-like Titanotheres developed in Wyoming. Each skull is known, 
by the stratum in which it was found, to be older than the one placed above it, 
to the right. 


THE EVIDENCE FROM THE ROCKS — 1938 


voleanic age, which was in contrast to our slow and 
peaceful era. We are familiar with the description of 
the earth as a fiery mass that cooled enough for a 
crust to form, though it was still molten inside, that 
finally cooled enough after an age of frightful dis- 
order to allow coal to form, that continued to cool and 
to thin its atmosphere until some animals could live on 
it, that cooled to an ice age, that will grow colder still, 
and that will at length freeze into a dead mass like the 
moon. Recent geology knows of no such process. Ge- 
ology tells us that as it was in the beginning it is now 
and, so far as can be foreseen, ever will be. No mak- 
ing of mountains in the past was ever much more 
spectacular than what is going on now right before our 
eyes. There have been ice-ages as far back as any 
record can be read in the rocks. Where the oceans and 
continents are now, there they have always been. The 
land masses have come and gone and come again, but 
always in the same general locations. Since its roman- 
tic beginning the earth has had a quiet history, almost 
monotonous. 

The modern geologist pictures the earth as made 
of a dense core, rich in heavy metals, kept hot by the 
work of its own gravity and by chemical action, and 
covered with a crust of lighter rock some fifty miles 
thick. Some form of adjustment is always taking place 
within this crust—not that it is ‘‘wrinkling like the 
skin of a drying apple,’’ but that parts of it are con- 
tracting and expanding as they adjust themselves to 
the shifting loads on the surface. Some heaving ap- 
pears to lift up masses of stratified rock—very gradu- 
ally, through long ages—on certain fixed lines of 
adjustment in the crust, and so to make mountain 
ranges. Then may come a compression which slides 
rocks for fifty or even a hundred miles from their 
first location, and tilts them as we see them in the 


194 EVOLUTION FOR JOHN DOE 


Alleghanies or the Alps. Recently geologists have 
learned that the material under a mountain chain is 
lighter than the material which underlies the regions 
on either side of the chain: the mountains seem to be 
counterpoised by denser portions of crust. In the be- 
ginning there were certain lines of adjustment—about 
where the greatest mountain chains now are—and 
there the mountains have usually been made. There 
were certain regions of depression—and there the 
deep oceans have always been. The changes in the 
earth’s surface have been a routine, a slow pulsing in 
certain regions. 

Though the alterations seem large to us, they are 
slight compared with the total bulk of the earth. The 
top of the tallest mountain is only six miles above 
sea level, a height which would be represented on a 
twelve-inch globe by no more than the thickness of a 
sheet of note-paper. 

As soon as a mountain range begins to rise, it is 
attacked by the water—worn down by friction, 
chipped by ice, decomposed chemically. Though it 
rises ever so high and is ever so hard, though the ac- 
tion of water seems ever so slight, the water will con- 
quer in the end; for water has as many millions of 
years as it needs to complete its destructive work. 
Slowly it carries away the pulverized rock, carries it 
as silt to the sea, and deposits it. As the thousands 
of years pass, the top of the mountain is being laid 
down in the bottom of the ocean. There it is subject 
to great pressure from later deposits, and to a ce- 
menting process. It is converted back into rock. 
Layer is formed upon layer. Thus an increasing 
burden is laid upon the shifty foundation of semi- 
fluid rock several miles below. Some time the strain 
will become too great to be borne, and then this new- 
made rocky bottom of the sea will be slowly crumpled 


THE EVIDENCE FROM THE ROCKS 195 


and lifted, perhaps only a fraction of an inch a year, 
into a new mountain chain—to be again worn down, 
and again raised up. 

Suppose that half a billion years is a correct esti- 
mate* of the time since the first animal left a record 
of itself in the rocks. Suppose that an angel had 
been commissioned to take a photograph of the North 
American continent, as it appeared at that time, from 
an altitude of several thousand miles, where a lens 
could command a view of the whole expanse. Suppose 
that every five thousand years thereafter the angel 
had taken another view of the same part of the earth 
from the same point. If the one hundred thousand 
negatives thus far taken could be put together in a 
single reel, they could be shown on a screen in an 
hour. Watching such a picture would be heaven for a 
geologist. What would he see? 

Imagine that a map of North America is traced in 
dotted lines on the screen, so that as we see the views 
of the ancient land masses we can tell where they 
were. Understand that the reel which we are to see 
begins when half of the rock-forming history of the 
earth had already passed. Of all the previous half- 
billion years of the continual heaving up and wearing 
down of land we can have small knowledge. But we 
do know that before our motion picture began thirty- 
two miles of sedimentary rock had been laid down in 
the ocean and raised above it, and that during the 


*Barrell’s estimate, on a uranium basis, of the time since lower 
Cambrian is seven hundred million years, and Schuchert thinks ‘‘this 
is excessive by fifty per cent.’’ (The Evolution of the Earth, Yale 
University Press, 1918.) The figures will seem excessive to most 
readers, because they are five times as great as those given in most 
recent books of reference; if they are too high, they will be the first 
estimate that ever erred in that way. See the 1922 Britannica, article 
Palaeontology. The data for the sketch of the configurations of North 
America since Cambrian time are in Grabau’s Teaztbook of Geology, 
Part II. 


196 EVOLUTION FOR JOHN DOE 


time of the picture only twenty-one miles of rock 
were made. 7 

As a prelude to the main reel comes a one-minute 
picture which gives two glimpses of the era before 
the Cambrian and indicates that we are plunging into 
the middle of the total history. It is a close-up of the 
Great Lakes region. A sheet of ice stretches down 
from the north to the American border, its ragged 
southern edge quivering back and forth; after ten sec- 
onds we can see that it is retreating, as the tide goes 
out with a series of advances that are farther and ~ 
farther down the beach. The ice disappears to the 
north. There is a heaving up of land. Then near 
where Lake Superior now is a volcano pours out 
smoke; another appears to the north of Lake Huron; 
great sheets of lava, hundreds of feet thick, cover 
wide areas. In them, if we could but see, are the cop-- 
per and silver that are now being mined in those 
regions. 

The picture closes and there is an interval. Then 
the main reel begins with some blocks of land that we 
should never recognize as our continent if the dotted 
lines of the map did not guide us. There are three of 
them: the largest stretches from north of the Hudson 
Bay region, tapering to a point in southern Mexico; 
the second is at the left, a block corresponding to Alas- 
ka and stretching southeast where the Canadian 
Rockies now are; at the bottom is the third block, 
where the West Indies now are, stretching in a slender 
northeasterly neck across to England. Long arms of 
the sea separate the two smaller land masses from the 
large continental one. 

You watch the lower end of the great central con- 
tinent slowly disappear, and the channels on either 
side of it widen slightly; the sea encroaches* some- 


*So it appears on the screen and so the geologists speak of it. 
What actually happened, of course, was that the land sank. 


THE EVIDENCE FROM THE ROCKS 197 


what on all the land for two minutes. Then for two 
minutes you observe that the sea is retreating and 
the land extending. During the following two minutes 
the changes are greater, for the whole southern third 
of the central continent is eaten away, and the other 
two blocks alter their shapes, becoming somewhat 
smaller in area. You do not find this entertaining. 
In seven minutes of the monotony you do not see as 
much change as an animated cartoon ought to show in 
three seconds. You shift in your seat and wonder 
whether anything worth while is going to happen dur- 
ing the next seven minutes. The learned lecturer tells 
you that you have now seen the whole of the great 
Cambrian period and are well into the still greater 
Ordovician. You are not thrilled. 

Still there is more doing on the screen. You see 
the central continent creep farther and farther south, 
widening as it goes, filling the arms of the ocean on 
the east and west, taking on an almost familiar ap- 
pearance: you can see a Gulf of California, a San 
Francisco Bay, a Puget Sound, and a Mississippi 
River. But the Gulf of Mexico opens toward the 
southwest, and a river twice as long as that ancient 
Mississippi runs from the state of Washington 
through Oregon and Nevada and Arizona. Now the 
ocean begins again to eat the land away, opening up 
the arms on either side of the continent and washing 
out a large gulf through Illinois and on through Iowa 
and Nebraska. At length it cuts clear across to the 
Pacific Coast, and runs a wide arm north through 
Wyoming to the Arctic Ocean. The continent be- 
comes a set of islands. So for a minute it remains. 
Then the land begins to grow, until a fairly respecta- 
ble continent emerges, stretching unbroken from 
northern Alaska to a tapering point in southern Mex- 
ico. ‘‘The close of the Ordovician,’’ the lecturer an- 


198 EVOLUTION FOR JOHN DOE 


nounces; ‘‘now note how the sea begins to wear down 
the continent and carve a north-and-south channel 
through it at the opening of the Silurian. The 8i- 
lurian will last four minutes.’’ 

As a movie, this sort of display on a screen would 
not draw crowded houses. Yet any one with imagina- 
tion has spent an extraordinary quarter-hour, watch- 
ing the rocks come and go with the slow lapse of 
millions upon millions of years. Every second of this 
picture represents one hundred forty thousand years 
—ten times as long as the whole recorded history of 
man. A minute of these motions on the screen is 
longer than the mind can conceive—more than eight 
million years. Our quarter of an hour has meant 
fifteen times those eight million years, and yet that 
whole inconceivable extent of periods is but one chap- 
ter in the whole volume of the ages of the world. 

We have seen on the screen nothing but the com- 
ing and going of land. What about life? When the 
reel opened, life was already far advanced; there were 
beautiful scallop shells and jelly-fish and complicated 
erab-like animals. For aught we know these forms 
had been developing from simple one-celled animals 
during a whole half-billion of years. In the quarter 
of the motion-picture that we have seen the corals 
developed, and the chambered nautilus, and a kind of 
fish. So much advance to show in one hundred thirty 
million years! 

Somehow, when we realize what this picture 
means, the remaining minutes of Silurian time will 
not utterly bore us. It represents twenty-five million 
years, during which the ocean three times reduces the 
size of our continent, and three times is slowly driven 
back by the rivers that pile sediment along the shore. 
There is a fascination in seeing this portion of the 
earth’s crust pulsing back and forth, never entirely 


THE EVIDENCE FROM THE ROCKS ~— 199 


consumed in the waters of ocean, always returning 
to that shape that tapers off at the south in the famil- 
iar Mexican outline, always showing some sort of 
Alaskan and Canadian and West Indian land, always 
showing a tendency to gulfs where gulfs are now. 
And there should be wonder in our hearts as we recall 
that this history was never revealed to geologists by 
an angel. No, they had to pack burros and wield ham- 
mers and draw maps and study specimens and com- 
pare notes and show up each other’s mistakes for a 
century before they could piece together the frag- 
ments that we are seeing by the grace of heaven. ‘‘If 
in this shale there is such a species of fish, and if this 
sandstone underneath it is of so coarse a texture, 
then’’—by comparing thousands of such inferences 
they slowly built up the knowledge of where the ocean 
was at different periods. Fishes are not adapted to 
desert life, and ferns never grew in the sea; each 
fossil of such an adaptation as a fish or a fern shows 
what the environment must have been for that form 
of life at that time. There is no more mystery in 
reading the geological record than there is in reason- 
ing that an old oriole’s nest was made by an oriole. 
All that is required is infinite care and patience, driv- 
en by curiosity. 

The records of the Silurian, and of the Devonian 
that occupies the next four minutes, show only one 
marked advance in organic life: cerae fishes devel- 
oped lungs, and so could live on the land. Plants 
also adapted themselves for living on land. At the 
times when the ocean was driven back there were 
likely to be certain bays that were filled across the 
mouth; the water-dwelling plants and animals that 
were thus cut off from the ocean would perish as the 
water grew brackish and finally evaporated. But if 
any organism varied in such a way that water became 


200 EVOLUTION FOR JOHN DOR 


less and less necessary to it, and if these variations 
were inherited and increased, that species could in 
time become adapted to live altogether on land. It 
would survive, while all the others would become ex- 
tinct. Such development came about some time dur- 
ing the last two periods that we have seen on the 
screen. It was momentous. Life then escaped from 
the sea and began its career on land. 

Now for eleven minutes you may watch the sea 
eat out the top of North America in a great gulf that 
reaches down to Mississippi and east into Pennsyl- 
vania, and then retreat again. A close-up of this new 
land left by the retreating sea shows that it is covered 
with a strange forest, composed of forms like our 
modern ferns and horse-tails and ground pine, but 
maenified to large trees. It is a riotous growth of 
the plants that have learned to live on land and that 
have waxed gigantic in the rich, new, low, swampy 
soil. As the trees die, the trunks and leaves form a 
kind of peat-bog that is transformed and compressed 
into coal. Insects swarm in the forest—some early ele- 
mentary kinds of bugs and beetles, cockroaches, and 
especially darning-needles, some of them thirty inches 
long. There is a reptile that reaches a length of eight 
feet. 

The semi-tropical growth fades away. The land 
rises, and the climate becomes cold. Those animals 
that have been well adapted to the warm moist condi- 
tions are in hard case to survive. Many must perish. 
Lucky are the animals that now have variations which 
fit them somewhat better for the struggle with a harsh 
environment. This five-minute period* causes rapid 
evolution of new types. A chart of the animals. 
through the ages widens out suddenly at this section 
into many kinds of short-legged, lizard-like reptiles. 


*The Permian, 


THE EVIDENCE FROM THE ROCKS ~~ 201 


During the thirty-six minutes of this picture that we 
have seen—and during a whole previous reel that ge- 
ologists can never see—life has been developing; and 
has progressed only as far as a big lizard. It is the 
early stages of any development that require time. 

From now on* the changes of the land will be 
quicker and seem more significant. During the last 
six minutes it comes back to almost its present shape, 
and remains so. In the last quarter of a minute of the 
performance you see a spectacular ice-sheet come 
down jerkily almost to the Ohio and Platte Rivers, and 
then retire. It was this that left the hills of pebbles 
on the Nebraska farm. And man in this picture? He 
was on the globe during the last second or two; civil- 
ized man has been here a tenth of a second. 

A few views of the animals during those last twen- 
ty-four minutes would furnish entertainment.t For 
fourteen minutes we could watch the reptiles increase 
in size, till some achieve a length of a hundred feet; 
and some grow heavier than four big elephants. They 
walk principally on their massive hind legs, which are 
midway between the long neck and the tapering end 
of the long tail. There are many other types of these 
‘‘dinosaurs,’’ and all varieties of other sorts of large 
and small, smooth or horned, lizard-like animals. It 
is the age of reptiles. From one species of these the 
birds developed, from another the earliest mammals. 
Other reptiles remained reptiles, and are with us to- 
day—crocodiles and horned toads and turtles and 
snakes. And all the other reptiles? They died out. 

There could be a picture of the progress, during 
the last six minutes of the reel, of a little animal only 
a foot high that walked on five toes. Its four side 


*That is, after the Paleozoic. 


tO. H. Ditmars has made, and shown to enthusiastic college audi- 
ences, a2 moving picture of animal evolution, 


202 EVOLUTION FOR JOHN DOH 


toes grew smaller; its middle toe grew longer and 
longer; it increased in size until it was five feet tall, 
and became the modern horse. The paleontologist has 
been able to reconstruct other histories, quite as re- 
markable, of insignificant animals that developed dur- 
ing these same periods into the camel and the elephant. 
The stages of their growth are in the rocks, as surely 
labeled and dated by accompanying fossils as if they 
were classified for us in a museum. Yes, they are 
more reliably recorded; for naturalists make mistakes, 
but nature never does. 

When any man has learned the alphabet of the 
fossils and is familiar with its grammar and idiom, he 
reads with assurance the history that has been pre- 
served in the volumes of stone. It is written in the 
language of the Evolution Theory—more consistent 
and indubitable than any chronicles that come down 
to us in Latin or Greek characters. It reveals how 
every form of life descended from some earlier and 
simpler form. 

The whole of the evidence in the rocks is vast be- 
yond comprehension and makes bewildering demands 
on our mind. To any reader who knows no more of 
it than I can compress into this chapter it must seem 
somewhat unreal. As an indication of how actual and 
vivid it all is to men who spend their lives with it, I 
will give a description of a scene that has recently 
been uncovered in southern California. If you could 
drive west from Los Angeles over a boulevard, and 
step out of a car at Rancho La Brea, and walk 
through the dry fox-tail grass to look into a certain 
excavation in a bed of tar, you would feel the reality 
of geology. 

All along the coast there are these outcroppings 
of asphalt, that has seeped through the shale and in 
some places formed deep pools of an extremely sticky 


THE EVIDENCE FROM THE ROCKS ~— 203 


substance, which can be dug out only by using heated 
shovels. The edge may be covered by soil and become 
hardened, while the center remains tarry. Shortly be- 
fore the World War an excavation was made in one of 
these pits, near Santa Monica, and there was discov- 
ered such a dramatic cluster of fossils as has never 
been seen elsewhere—saber-tooth tigers and elephants 
and mastodons that had been caught in this death- 
trap, mired in it, sunk, and been perfectly preserved. 
If I should find my horse dead in quicksand, I should 
not know more certainly how he died than I know 
when I look into this pit how these tigers died. The 
men who study oil shales know, as a matter of prac- 
tical business, in what geological period the asphalt 
was made. It is a certainty that during the last min- 
ute of our reel elephants mired down in the California 
tar and trumpeted their distress, and that they were 
heard by a kind of tiger that no longer lives on earth, 
and that the tigers were attracted, and mired down to 
their death. The contorted bodies tell their story as 
plainly as a charred corpse in a house of Pompeii, 
covered with volcanic ash, tells how the man died. 
The episodes of all the history of evolution in the 
rocks have come from scenes which, though not so 
romantic, are as unmistakable as that in the asphalt 
pit. 


CHAPTER XIII 
THE EVIDENCE FROM GEOGRAPHICAL DISTRIBUTION 


WHEN acertain entomologist had studied a genus of 
beetles from Colorado south into Mexico, he prepared 
a chart showing where the different species live. 
‘The study of the chart,’’ he says, ‘‘gives clear ideas 
as to what the course of evolution has been.’’ This 
little example will illustrate the experience of all 
modern naturalists when they map the locations of 
animals. If you could remove from their minds all 
knowledge of how species originate from previous 
species, their charts would have no meaning; all the 
groupings of animals would be a disorderly jumble. 
But the combined labors of collectors fit together 
into an orderly whole of animal life when evolution is 
understood. 

To every modern naturalist the term ‘‘distribu- 
tion’’ is a pictorial way of saying ‘‘evolution.’’ If we 
eould look at the world of life through his eyes, we 
should see that any great class of animals, such as the 
insects, is everywhere over the globe; to make a chart 
of them would be simply to draw a complete map of 
the land surfaces of the earth, except for those few 
areas where there is no life of any kind. Even one 
division of this class, say the order of beetles, would 
be spread almost as widely. But any one family of 
this order, the leaf-beetles, for example, would be ab- 
sent from some desert areas where other families 
have found a way to live. Any one genus of this 

204 


GEOGRAPHICAL DISTRIBUTION 205 


family flourishes chiefly on one continent; it is to be 
found in only a part of the region that the family 
covers. Any one species of this genus—for instance, 
the potato-beetle before it found potatoes to eat—is 
restricted to a part of the territory occupied by the 
whole genus. When the range of any one species is 
thoroughly known, and its varieties charted, it ap- 
pears that the species is most uniform and constant 
in the center of the range, and that the distinguishing 
characters fluctuate more and more in proportion as 
the specimens are gathered farther from that center. 

The chart of the range of the species of any large 
- genus of animals always shows a similar fact: there 
seems to be a center of the most typical forms, from 
which many species radiate; and each species radiates 
from its own center in varieties. If the naturalist 
assumes that each species is a group which developed 
from a preceding species, and that all the species of a 
genus branched out and pushed afield from some com- 
mon ancestor, he can understand the distribution of 
animals. If he tries to imagine any other explana- 
tion of the locations of the different groups, he comes 
to grief. 

All the facts of distribution point toward one fact 
—that the species of animals always develop by mi- 
grating continuously from their centers. Just as the 
evidence from the rocks shows that all organisms have 
developed continuously in time, from one age to an- 
other, so the evidence from distribution shows that 
they have spread by steady advance from a center 
where they originated. The chapters on classification 
and structure will show other phases of the evidence 
that life is always continuous in its lines of descent 
and location and classification and structure. The 
central truth of all the evidence in Part Two is that 
organic life, from whatever point of view we examine 


206 EVOLUTION FOR JOHN DOE 


it, appears as a continuous whole. We can not explain 
such a many-sided truth except by the theory that 
every form descends from a previous form. 

If a zoologist finds some specimens of a certain 
species in Vermont and some specimens of the same 
species in Ohio, he can not conceive that they are un- 
connected. All the evidence of distribution declares 
that the species must live—or that eggs must have 
been transported, or that individuals must at some 
time have lived—continuously all the way from Ver- 
mont to Ohio. There is no evidence that the same 
species has ever originated in two places; it has only 
one origin, in one place, at one time; and from that 
origin it has spread out as far as it could go. And as 
a species spreads from its original center, it tends to 
alter, adapting itself to the new environments that it 
comes into. The whole theory of evolution would re- 
ceive a severe shock if the facts of distribution did not 
always indicate that development has been continuous 
in time and place. 

An illustration of the evidence that comes from 
distribution is seen in an exhibition of snail-shells in 
the American Museum of New York. They were col- 
lected in the island of Tahiti. The genus to which 
they belong has various species on many islands, but 
the five species in the exhibit are found only on Tahiti.* 
Hach of these appears as a pushing, branching, vary- 
ing group of forms. Number one has pushed into al- 
most every valley, and nowhere varies much in its 





*The New York Times of April 20, 1925, gave a striking account 
of what Professor H. E. Crampton, of Barnard College, had discovered 
about Partula on the island of Moorea, near Tahiti, ‘‘One of the three 
varieties found in 1909 had spread over the entire island. Its different 
valley colonies had become greatly diversified in size and color, pre- 
senting types unknown in 1909.’’ Professor Crampton’s earlier re- 
searches are in the splendidly illustrated Carnegie Publication No. 228, 
1916; his later work is reported in The American Naturalist for Jan- 
uary, 1925. 


"90zZ osed 900 
‘£IOJLLIOY LAPUA THAO PBards ovavy Sotoods ouloOSs puB ‘padoaAdp IABY SOTOLMVA MoT SIBIOA AJUOMY JSBL OY} Surinqg ‘Tyyey, 
Jo puBsyT 9} UL S[IVUS JO SNUDS B JO SUOTIBIUBA JY} GUTMOYS ‘UNESNI UBIO YW oY} UL JIqtyxes uB Jo ydersojoyg 





Sona, 


S THE 
SALAP ASHE ESAS 
SOE THEA SNIMALS 


2 Be ioaasnae Beem aon iba Nee 
socks 668 noo 6 ee UR FON ES 
oot co cases ooo mnonoonl on rs 88 
‘he Roms eepeck- Seg. ats, sete Ta A: 
Bae ee 


Sth: Sete a CRS MEAS 





Another American Museum exhibit of the evidence that com i 

nee es from geograph 

distribution—the finches in the Galapagos Islands, where Darwin aot a aati 
studies of evolution. See page 213. Z 


GEOGRAPHICAL DISTRIBUTION 207, 


white color; whereas number two is confined to one 
valley. Number three ‘‘has recently extended its 
range and differentiated into four varieties.’? Num- 
ber four ‘‘has recently migrated and differentiated 
into varieties.’’ Hight varieties of the wide-ranging 
number five have been found. If these descriptions 
of what the shells have been doing were the fancy of 
some one collector, we should pay no attention to 
them; they would mean nothing: But the same kind 
of description comes nowadays from all students of 
all kinds of animals everywhere. 

Another graphic display of distribution is a large 
map of the western half of the United States, on which 
are the skins of eleven species of striped ground squir- 
rels that range from Oregon to Wisconsin. The great 
family which embraces all the squirrels is world-wide, 
though it is strongest in North America. This genus 
on the map (Hutamias) ranges over only part of the 
United States. Hach species is limited to a part of 
the whole area of the genus. When a scientist sees 
the large dark pelt of one species change through a 
series of species across the map to one that is light- 
colored and small, he reads a record of branching out 
from a parent stock and of altering to adapt to the 
new environments that were met as the genus spread. 
Every chart of every successful genus always reveals 
the same fact. When specimens are arranged accord- 
ing to where they live, they present a series of graded 
forms, as if their genus were a source of variant life 
that was forever trying to propel itself farther away, 
and that altered as it moved. 

‘‘Harther south,’’ says one naturalist’s report, 
‘“‘the species degenerates in size and is obscurer in 
color.’?’ That matter-of-fact statement would have 
been queer jargon to Darwin in his boyhood, for it 
represents a group of forms as a fluid, fluctuating 


208 EVOLUTION FOR JOHN DOE 


mass that changes while it grows toward a new habi- 
tat. But to the Darwin of middle life it would have 
sounded like a perfectly natural description, because 
a species at one end of a wide range is bound to be 
different from what it is at the other end. ‘‘In dif- 
ferent localities,’? says the naturalist, speaking of 
another species, ‘‘it tends to the development of dis- 
tinct local forms.’’? Every study of distribution, of 
any plant or animal, shows the same tendency. 

We have been attending to some petty examples. 
Take a very large one, as stated by Professor H. F. 
Osborn in 1900: ‘‘The fact that the same kinds of 
mammals and reptiles appear simultaneously [1. e., 
during the same geological periods] in Hurope and in 
the Rocky Mountain region is strong evidence that 
the dispersal-point is half-way between.’’ He pre- 
dicted that such an origin would ‘be found in Asia, 
and he named the fossils that must some day be 
searched for there. In the spring of 1922* the Amer- 
ican Museum expedition to Mongolia began to find 
them, and in generous measure. When any theory of 
distribution has produced such successful prophecy 
as that, it is well tested. 

The greatest test of the theory is on the islands. 
Some of these are very close to a mainland, and some 
are very remote; some have been separated very re- 
cently, and some for several geological periods, and 
some never were connected with other land; some 
could be reached by immigrant animals of certain 
sorts, but not by other sorts; they might preserve old 
species with little change, or they might force old 
species to develop new adaptations. Thus they are 
like experiment-stations established in the ocean to 
give proofs of whether or not all species develop by 
continuous descent and in continuous lines of migra- 


*Still more striking discoveries have been reported in 1924 and 1925. 


GEOGRAPHICAL DISTRIBUTION 209 


tion. If evolution were not true, its falsity would be 
sure to appear in some of the facts of animal life on 
islands. If it is true, then the following conditions 
would have to be found: 

1. There would never be upon an island an ani- 
mal whose ancestors had not reached the island. 

2. In proportion as islands are farther from a 
mainland, or have been longer separated from it, the 
animals on them should be more different from those 
of the mainland. 

3. But in some cases (for example, if some fierce 
competition of the mainland were removed on the 
island) we should expect to find that species had al- 
tered less on islands than on the mainland. 

4, The kinds of animals would, in a general way, 
be numerous in proportion to the ease with which they 
could reach the island—for example, by flying, swim- 
ming, being borne in currents, being drifted by gales. 

The facts of the distribution of animals on islands 
are in accordance with those conditions, as the fol- 
lowing descriptions will show. 

Long Island is detached from the mainland by 
only half a mile of water, and the separation was 
made in very recent times. Hence we should expect 
that the animals and plants on it would be only very 
slightly different from those on the mainland. That 
is the fact. When it became an island, it was stocked 
with the same species that were on the New York 
shore; and it has been so close to that shore that there 
could be much migration. There has been little time 
for new varieties to develop, and there has been only 
partial isolation from the life that swarms on the 
mainland. 

If you go eight hundred miles southeast in the 
Atlantic, you come to the Bermuda Islands, twenty 
square miles of low-lying limestone hills surrounded 


210 HVOLUTION FOR JOHN DOE 


by coral reefs, a small remote bit of land that has 
long been separated by hundreds of miles of water 
from the nearest Bahamas. Here we should expect 
to find the animals very different from those of our 
nearest Atlantic coast and somewhat different from 
those of the Bahamas. Such is the case. There is 
only one backboned animal which is native, a lizard 
that is found nowhere else in the world. Yet among 
the birds there are no peculiarities—no species that 
is not found on the mainland. Among the shell ani- 
mals and insects, however, there are extraordinary dif- 
ferences—a great array of peculiar species. <A zool- 
ogist who reasons about this problem of distribution 
asks, ‘‘Why should birds be just the same as on the 
mainland, while the reptile is a solitary curiosity and 
the shell animals are widely different?’’ If he could 
find any sensible explanation that did not depend on 
the evolution of species, he would become famous; and 
there are hundreds of eager scientists who would be 
glad to work unremittingly many years for such a re- 
ward. But no zoologist ever wastes a precious hour 
on such a mad venture. He would have a better chance 
of finding out how to control thunderstorms than of 
finding a non-evolutionary clue to the assemblage of 
animals in Bermuda. | 
If every species has developed from a previous 
species by gradual alteration, and if every species is 
a varying group of life that is always prone to adapt 
itself in old surroundings or in new ones, then there 
is no mystery about the life of Bermuda. When the 
large continental island east of our coast, ‘‘Antillea,’’ 
was broken up into fragments during the last great 
geologic era, the northernmost bit that became Ber- 
muda was stocked with the same genera that had pop- 
ulated the whole of Antillea, but that had varied a 
good deal since Antillea was, long previously, sepa- 


GEOGRAPHICAL DISTRIBUTION 21T 


rated from the main continent. Then the species, in 
their isolation, entered upon a period of separate 
development. Some kinds of animals had been sparse- 
ly represented in this northern tip: lizards had been 
so scanty that only one species has survived to our 
time, and it has altered to a unique form. Of the 
abundant shell-fish many have remained practically 
what they were; many have branched into varieties; 
many have changed so far as to become new species. 
The same history holds for insects. For many ani- 
mals Bermuda has been an isolated home: they could 
not leave it, and others of their kind could not reach 
it. But many shell-fish and insects and seeds have 
from time to time been brought from the southwest 
by gales and the ocean currents, and have thus re- 
plenished the local types. No snake or warm-blooded 
animal ever has survived such a long ocean journey 
to propagate its kind. As for birds, they have no 
more been cut off from Bermuda than they have been 
from Cuba or Georgia; in their migrations they visit 
it regularly; and hence there has been no more reason 
for the development of a new species on the islands 
than there has been on the mainland. When geology 
and evolution are applied to these islands, they fur- 
nish an understanding of the history of life there. 
Without evolution no rational history can be con- 
ceived. : 3 
The Azores are more isolated than the Bermudas. 
From water that is two and a half miles deep, in mid- 
Atlantic, they rise, not a thousand square miles of 
area, in complete isolation—eight hundred miles from 
the nearest point of Europe, nine hundred from Af- 
rica, and one thousand from North America. The life 
on these islands would be an impossible enigma with- 
out evolution. When that theory is applied, all can 
be understood. One kind of bird has long made the 


212 KHVOLUTION FOR JOHN DOH 


Azores its home, and it has become a unique species; 
but otherwise the birds are not peculiar. Most of 
the insects and shell-fish are like those of Kurope; 
some have been much modified; all could have been 
immigrants borne by the accidents of storms and cur- 
rents. No backboned animal without wings is to be 
found there except those that have been brought by 
man. The islands have been almost entirely stocked 
with European forms of life, some of which have al- 
tered into new varieties and species. 

It will be safe to say at this point that for sixty 
years there have been sagacious zoologists who wished 
to find some problem of island distribution that evo- 
lution could not solve. We laymen are almost sure 
to suppose, even after many repetitions, that ‘‘the 
scientists’? have determined to support their pet the- 
ory and to adjust all the facts of island life to fit it. 
Doubtless some of them have had that attitude. But 
all the while there have been many more ready to 
challenge and oppose the theory. During the sixties 
most of the older naturalists were in that camp, and 
they bent their energies to show that evolution was 
not necessary to unriddle the Bermudas and the 
Azores; they figured out ‘‘land bridges’’ and ‘‘dying 
out of species’’ and other possibilities to account for 
the facts. No modern geologist can find any support 
for their theories. No modern scientist knows of any 
way to understand the species of the Azores except as 
a gradual change of species into other species. 

Jf a summary is made of all the facts known about 
the distribution of life on voleanic islands, there is 
always confirmation of evolution; and there is never 
any crucial evidence against it. Men have seen islands 
so recent that not a vestige of any life was on them. 
On other very recent islands there have been seen 
specimens that have been carried from the nearest 


GEOGRAPHICAL DISTRIBUTION 213 


land and that are identical with the species on that 
land. No life has ever been known to originate on a 
new island; it is always brought there as a continua- 
tion of previous species. Most of the immigrants to 
new land come from the nearest islands, or they are 
preponderantly from the mainland. There 1s never 
any species that might not somehow have arrived at 
that shore from another shore. When animals have 
been for some time in this new home—even for so 
short a period as a hundred years—their variations 
begin to take effect. Quite marked varieties have 
been seen in rats and pigs and rabbits, even during 
the three centuries that men have been able to observe 
such changes. Every peculiarity in the distribution 
of life on islands is consistent and comprehensible on 
the theory that no species ever originates without an- 
cestry and that most species tend to alter gradually 
and to send off new varieties, which will become new 
species if time is long enough. The composite pic- 
ture of the distribution of plants and animals on is- 
lands is like a photograph of evolution. No details 
gathered from Hawaii and the atolls of the South Pa- 
cific and Iceland are discordant with the picture; all 
fit into place as part of a rational scheme of things. 
A classic example of island life is that in the Ga- 
lapagos, more than five hundred miles west of Heua- 
dor. When Darwin landed on them, long before he 
believed in any theory of evolution, he was struck by 
the similarity of the life to that of the mainland. 
‘*Almost every product of the land and water,’’ he 
reported, ‘‘bears the unmistakable stamp of the 
American continent.’’ The conditions of life there 
were not very similar to conditions on the mainland; 
they had more resemblance to the climate and soil of 
the Cape Verde Islands, which are off the west coast 
of Africa. Yet the life of the Cape Verde Islands is 


214 HVOLUTION FOR JOHN DOE 


African in character, and the life of the Galapagos is 
South American in character. A good observer can not 
resist the conclusion that each group of islands has 
been stocked from the neighboring continent. If he 
tabulates the evidence from all islands, he finds his 
conclusion strengthened by everything that can be 
learned. Nothing has ever appeared that contradicts 
the conclusion. And another conclusion is quite as in- 
evitable: most of these animals on the Galapagos are 
not now the same as when their ancestors migrated, but 
have altered so far as to have become new species. 
The evidence of distribution on islands always points 
one way. | 

The most remarkable confirmation is the great 
island of Madagascar. It is separated from Africa 
by only two hundred fifty miles of water, and yet its 
life has much less resemblance to the African forms 
than the life of the Azores has to Kuropean forms— 
though the Azores are four times as far away from 
Kurope. Why should evolution have anticipated that 
this would be the case? Because Madagascar has 
been separated from Africa vastly longer, and there 
has been time, in its large territory and differences 
of environment, to develop greater differences of 
form. 

Madagascar has also preserved many types that 
are nearer to their ancient ancestors than any species 
that survived in Africa. It is like a museum where 
the naturalist may see forms that he could only have 
conjectured from the animals that now live in Afriea. 

The greatest collections of these zoological an- 
tiques are in New Zealand and Australia, where the 
animals that bear their young in pouches (the mar- 
supials) are the dominant type. There was a time 
in geological history when the marsupials were 
common over the world; but they have become extinct 


GEOGRAPHICAL DISTRIBUTION 215 


(except for the opossums) everywhere but in New 
Zealand and Australia. There, cut off from the rest 
of the world, they have developed into flesh-eating 
animals that look like wolves, into gnawing animals 
of a rat-like appearance—in fact, into forms that out- 
wardly resemble almost all the orders of placental 
mammals. The animal distribution in Australia is to 
the evolutionist what a discovery of an Hgyptian tomb 
is to the historian; it sets before his eyes the facts 
of bygone ages. 

When geologists map the fossils, showing in sum- 
mary form where the different kinds lived at different 
periods, the distribution in past eras tells him the 
same story that is everywhere attested on the islands 
at present. If a naturalist charts the habitats of birds 
or of wasps or of mastodons, he finds that he has 
made a sketch of evolution. If a botanist maps the 
pines or orchids or palms, the sketches of their dis- 
tribution are sketches of evolution. Knowledge of 
distribution always strengthens the assurance that 
animals and plants have been developed by a process 
of evolution. 


CHAPTER XIV 
THE EVIDENCE FROM CLASSIFICATION 


Last year a celebrated lecturer dared to make this 
statement to an audience: ‘‘There are myriads of 
living creatures about us, and yet not one is in transi- 
tion from one species to another; every one is 
perfect.?? He will never know how untrue his 
declaration was. And even if he were curious 
about the facts of the case, it would be hard 
to show him his error, because the reality is 
so different from anything that he cares to talk 
about. In fact, he has stated a half truth that 
ean not be flatly denied, and it is the particular half 
truth that has caused the most skepticism about evolu- 
tion. It is worthy of a full explanation. 

If a college boy were debating with him, the most 
telling retort would be to ask, ‘‘Did any one ever see 
a stratum of rock rise from the ocean?’’ The answer 
is no. And yet any intelligent person must admit 
that strata have risen from the ocean; in some places 
we can see, with a strictly correct imagination, that 
rocks are now rising. It is so with species. 

But comparisons do not prove anything. Put the 
question to a botanist: ‘‘How can you believe that 
one species changes into another if you have never 
seen such a change?”’ 

He will answer: ‘‘Because we very seldom see 
a species stand still. Almost every species is varying 
right before our eyes. There is hardly such a thing 

216 


EVIDENCE FROM CLASSIFICATION 217 


as a fixed species that you can describe and count on 
and distinguish from all other species. They change 
and blend and weave in and out among each other 
so much that a botanist may find it hard to tell what 
any one species is. I might quote what an instructor 
of mine used to say about another topic: ‘You won’t 
understand it till you’ve lived with it.’ Select some 
small genus and live with it a while.’’ 

If you, unlike most people, care to spend a few 
hours with the genus of spruces, you can get at least 
an inkling of what the professor meant. You pull 
down your trusty Britannica and find eleven lines; 
only two species are named, and you are referred to the 
article on Fir. It appears that there are many genera 
commonly called ‘‘firs,’’ and that two of them have 
always been much confused. But you at least learn 
that the genus you are trying to find is Picea, and you 
see the names of three species. The encyclopedia will 
do nothing more for you. So you try the Century 
Dictionary. You learn that Picea and Abies have 
always been much confused, because the leading bot- 
anists have had different opinions about the best way 
to classify; but that the trees you know as spruces are 
now generally called Picea, and that the true firs are 
called Abies. That is queer. Last summer in the 
Adirondacks you saw no possibility of confusing the 
two. You learned readily to tell a spruce from a 
balsam fir and to recognize the hemlock and the pines. 
The four kinds of evergreens were ‘‘perfect species’’ 
and could not be mistaken for one another. To re- 
fresh your memory you look up hemlock. Strangely 
enough it is to be found only under ‘‘hemlock-spruce’’ 
and is defined as ‘‘an American fir.’’ Yet it is not of 
the genus Abies, but is of the genus 7’suga. If you 
now look up this genus, you will be on the trail of 
Pseudotsuga and will discover that ‘‘by Wichler, 


218 EVOLUTION FOR JOHN DOH 


Bugler, and others it is united with J'suga, and is 
variously called Oregon pine, Douglas fir, or Douglas 
spruce.’’ Since life is short, you step back from this 
snare and stick to the narrow road of Picea. It ap- 
pears that ‘‘Asa Gray and others included the genus 
under Abies, but that present usage calls the spruces 
Picea, which includes about twelve species.’’ Now 
why, in the name of all that’s orderly, should the dic- 
tionary say ‘‘about’’?? Why shouldn’t it count up 
exactly and say that there are eleven or fourteen? 

Don’t allow yourself to grow excited and to set 
your heart on finding out just how many species of 
Picea there are. For you never can know; nobody 
ever will know. The different forms of Picea 
could be lumped into seven species, or could be split 
into forty. A species is merely what a number of men 
think. Naturalists try, for their own convenience, to 
agree so far as they possibly can; but agreement by 
all classifiers is exceptional. Ask any botanist to 
name for you a species that is ‘‘perfect and distinct’’ 
from all other species. You might as well ask him 
where the Pacific Ocean ends and the Indian Ocean 
begins. 

Thus you have one preliminary peek at what class- 
ification means. Look a bit farther. Read the 
descriptions of seven species of spruce: black, white, 
Norway, Himalayan, tideland of the Pacific coast, 
engelmannt of the Rocky Mountains, and parryana, 
‘fa rare and local mountain species of the western 
United States.’’ If you look under ‘‘king-pine,’’ you 
will find a ninth species, webbiana. 

If you care to spend ten hours for a little more 
understanding of what classification means, you will 
discover that even a large inclusive genus of ever- 
greens is not definitely marked off from other genera. 
Jt is hard to follow the ins and outs of the characters 


EVIDENCE FROM CLASSIFICATION = 219 


of cones and leaves and bark, so as to find some one 
way in which all of a certain large group can be posi- 
tively distinguished. What holds good as a distinction 
between spruces and firs in New Hampshire and Idaho 
takes a backward twist in India. In the volumes of a 
big manual you can see how one botanist after another 
has spent perplexing years in assorting by some dif- 
ferent sets of characters what previous workers had 
arranged in another series. A genus is not a firm 
unmistakable type; it is like a fluid mass of life that 
flows among and interlaces with other related types. 

And a species! It is a set of opinions formed by 
men who have tried to group the principal variations 
of a genus of forms that shade into each other. Every 
botanist who deals with the genus wishes that the 
divisions of it could be readily told apart, but he sel- 
dom encounters a distinct species. When he completes 
his chart of a genus, he has made—against his will and 
with great labor—a display of variations that may be 
distinct at their opposite ends, but that blend where 
they meet. 

fivery person who is not a botanist takes it for 
granted that a spruce is a spruce. If he learns to tell 
a spruce from a hemlock and a balsam, he is proud of 
his knowledge. Then some day he may have to cut 
and trim a number of young spruces and peel them 
for tent-poles. They all look alike; unmistakably they 
are spruces, cut down within an area of six square 
rods. But he learns that the bark of one comes off 
easily in long strips, and that the bark of another 
clings so that it can only be hacked off in bits. As he 
observes these trees in his neighborhood, he realizes 
that they vary in the shapes of their tops, in the pos- 
ture of the limbs, in color. A dog would find that 
spruces differ in odor; a chemist would find that 
they have varying percentages of resin and sugar. 


220 EVOLUTION FOR JOHN DOE 


Within the species, as it grows in one district, there 
are varieties, which vary among themselves, until in 
the last analysis every tree is a unique individual. 

Suppose that some wealthy young man became 
engrossed in the genus Picea and determined to make 
a fad of it for some years; suppose that he followed it 
from Newfoundland to Oregon and around the world, 
taking his time to wander for many days in each 
locality, to make complete notes of variations in char- 
acters, to study constantly for some better scheme of 
classification of ‘‘about twelve species.’’ After 
three years of travel and examination he spends a 
year in studying all the available literature of the 
subject and noting the discrepancies and ignorance of 
all authors—not one of whom could spend so much 
time in this limited field. Now he is an expert. But 
realizing that his knowledge is narrow, he studies gen- 
eral botany for three years more, specializing on the 
conifers and writing a doctor’s thesis on a genus which 
is intermediate between Picea and Abies: ‘*The 
Paired Species of T'suga, a Study in Ontogeny to De- 
termine Whether Pattoniana is a Species or a Genus.”’ 
You see, classification is such a difficult art, requir- 
ing such a long and severe apprenticeship, that no 
man is fit to determine species of spruce until he has 
proved by work in allied genera that he is a competent 
observer and that he has good sense in reasoning from 
his observations. If our friend can show some acute- 
ness in his criticism of Professor Lemmon for erect- 
ing Pattoniana into a genus Hesperopeuce, he will be 
listened to respectfully when he proposes a classifica- 
tion for Picea. 

Just as he begins to prepare his monograph, his 
eye falls on a startling piece of news in a scientific 
journal: a new field of research has opened for all 
students of conifers—the fossil Bennettitales. It 


EVIDENCE FROM CLASSIFICATION = 221 


flashes upon him that during ten years he has only 
looked at the surface, that there are facts of woody 
structure and mode of cone-bearing that may shortly 
upset whatever he publishes. He reads: ‘‘We find 
ourselves profoundly ignorant of the values of the 
characters of living plants for differentiating species. 

. . There is difficulty in mastering the overwhelm- 
ing mass of living species with which the fossils must 
now be compared.’’ Still there is hope, for ‘‘In small 
genera of gymnosperms [of which the conifers are a 
part] the comparison may not be crushingly burden- 
some; Berry, Halle, Thomas, Bancroft, Antev, and 
others have already done pioneer work. . . . The 
detailed chemistry of different cell units is now grad- 
ually being correlated.’’ For a few days his spirits 
are low, and he meditates a return to. collecting 
postage-stamps. But courage returns. Here is a fas- 
cinating vista of difficulties to overcome. Perhaps if 
he studies geology and paleobotany and chemistry and 
recent cytology for five years, he may qualify to un- 
derstand what Berry and Halle and the rest are about; 
he might even join in their exploration of the cells of 
conifers that lived ten million years ago. If he signs 
for such a cruise into the distant realms of species, he 
will sail far beyond the bounds of this little elementary 
book on the outlines of the Evolution Theory. Of 
course he will never return to classifying spruces; it 
is a job so far beyond present knowledge that it must 
be carried out by the next generation. He will go on 
~ and on toward an understanding of how no species is 
ever distinct, but is a branching group of forms, which 
branched off from an earlier stem, which grew from 
a still earlier stem. He will never see in future—no 
scientist ever sees—a species that is ‘‘perfect’’ and 
that stands still to let itself be classified as a fixed 
form of life. : 


222 EVOLUTION FOR JOHN DOE 


You have seen one bit of an indication of what is in 
a botanist’s mind when a breezy layman asks, ‘‘Have 
you ever seen a spruce change to a birch?’’ He can 
only smile—if he is good-natured enough—and say no. 
In that sense no student of plants has ever seen a 
species, in nature, change to another species. But 
such a question is the merest crude ignorance. In 
every other sense the botanist sees species changing. 
Species have hundreds of times been brought from 
nature to cultivation and have branched off into 
widely different varieties in a few years. When the 
ancestry of a species is traced back in geology, it is 
seen as a stream that alters from one period to 
another. A species is no more an everlasting creation 
than a mountain, and no more independent. Mountains 
and species are made out of previous mountains and 
species. A carpenter could as easily believe that houses 
are miraculously made out of wood that never grew 
in trees as a botanist could believe that any species 
was ever made without descending from a previous 
species. 

The little experience with spruces could be dupli- 
eated with almost every genus of plants or animals. 
In some cases, of course, there is a whole genus—yes, 
a whole family—that is quite distinct from any other 
form that exists—such as the tuatera lizards of New 
Zealand or the horned hog of India. In the Field 
Museum of Chicago you may see a coon-like dog which 
is the only species of a genus, and an African rabbit 
that looks like a kangaroo, which is the only genus of 
its family. Such solitary types are just what we 
should expect to find sometimes if species change 
into other species; for there have always been groups 
that fell behind in the struggle for existence, that did 
not branch out into new forms, but gradually became 
extinct. The fossil record is full of such examples, 








Dacia Soca RE 








Tha Ancestry of the Horse tao 
heen traced hank through @ tony 


REACT Soa 





“HIND FOOT 


This series, showing the evolution of the horse, is the most famous piece of 
evidence discovered by paleontologists. See page 244. 








This mammoth was found in Indiana. Mammoths have been dug up in great 
numbers throughout the northern states. So recently have they become extinct 
that early men in Europe drew pictures of them. 


EVIDENCE FROM CLASSIFICATION = 2238 


There are in the world to-day many unique plants and 
animals that form the dying tip of a twig of the tree 
of evolution.* But otherwise, in the case of any type 
that is at all prosperous, there will be varying forms, 
impossible to reduce to order by any hard-and-fast 
lines of classification. Each type is like an area of 
life: in its center it is decidedly different from the 
central forms of other types; at its edges it melts into 
surrounding edges. 

When the classifiers of insects first saw the Hypo- 
cephalus of Brazil, their brains would have reeled if 
they had known nothing of evolution. Here was a 
monster three inches long that was composed of 
family elements apparently as dissimilar as the char- 
acters of the cow, the dog and the squirrel. What 
could be done with him? If classification had to deal 
with fixed species, there would be nothing to do except 
surrender. But if life is understood as a variant 
stream of forms, this strange creature has a place in 
a rational universe, and comes to our museum as a 
witness to the course of evolution of beetles. 

We have been long enough cramped in the limits 
of single genera. Take a flight into a wide region of 
classification and see what it looks like. One phylum 
would serve as well as another. Try sponges. We 
could guess that there must be several kinds of them, 
because some are so soft and some are dark and 
coarse. Take three years off for the study of them. 

They live on every seacoast. If you should decide 
to amuse yourself by classifying them without reading 
what zoologists have learned during the past century, 
you would hardly make a beginning on the Gulf of 
Mexico in three years. By that time you might find 
out that you could not tell the difference between one 
sponge and a hundred sponges. It is not possible to 


*See the diagram on page 187. 


224 HVOLUTION FOR JOHN DO 


decide surely on any dividing line between an indi- 
vidual, all of whose cells work together as your own 
cells do to make one individual, and a colony of 
sponges which remain separate individuals. Some 
species are clearly of one type and some are clearly of 
the other; but the two types blend. 

Do you begin to weary of the ‘‘blending”’ of types? 
That is what every classifier wearies of. He can not 
count on finding any border to any type that seems 
distinctive. This great tribe, A, is absolutely distinct 
from another tribe, B; and you suppose for quite a 
while that they have nothing in common. But as you 
gain knowledge, you discover that A is not fixed; you 
gather specimens that form a continuous series, shad- 
ing off from it toward the B type. The same is true 
of B: it shades toward A. They blend. In proportion 
as a group seems constant, it is small and unsuccess- 
ful; in proportion as you will find it wide-spread and 
victorious, its forms are variant. 

If you are sagacious and persistent, you may learn 
after twenty years that there is a fairly well marked 
division of all sponges into those that have limy skele- 
tons and those that have flinty skeletons. The first 
group is small. You distinguish two kinds of them: 
(a) those that are lined with protruding cells; (0) 
those that are lined, partly at least, with a smooth 
floor of cells. Even in this 6 group—much the smaller 
one—there is crisscrossing with a third group, some- 
what unlike either a or b, so that you are in despair 
about them. As for the flinty sponges, it will take you 
months to arrange the descriptions of them from your 
hundreds of note-books; and when you have made a 
preliminary assortment on the basis of the cells with 
which they are lined, it won’t do at all. You see 
another possibility: perhaps you can classify them by 
the hardness and softness of their skeletons. 


EVIDENCE FROM CLASSIFICATION 


220 


If you persevere, reading the great treatises that 
scholars have made, and repeat your observations for 
several years, then you will understand that a fixed 
species hardly exists in nature, that a species is a 


compromise of opinions. 


For a century men have been at work on sponges. 
So far the classifiers can not agree on any mode of 
arranging the phylum. It would appear a wanton and 
meaningless mass of unreason if we did not under- 
stand that every form has branched from a previous 


different form and tends 
to continue to branch in- 
to new forms. With this 
knowledge for a clue, spe- 
cies are being assorted, 
and some time they will 
be straightened out. As 
more is learned in other 
departments of zoology 
about the principles by 
which forms evolve, the 
knowledge can be applied 
to throw light on sponges. 
No zoologist nowadays 
ean conceive of classify- 
ing by any other clue. By 
it he is led to understand- 
ing; without it he gropes 
and stumbles in the dark. 

A glance at the diagram 
of one classification of 
the sponges will illustrate 
how all classifiers con- 
ceive their business in the 
twentieth century. All 
life is thought of as as a 





Lithistida 


Protoly nthus 


Chart, after Dendy, of the classes 

and orders of the sponges, which 

have furnished specially interest- 

ing evidence of lines of descent 

from extinct forms. Compare this 

with the chart of a sub-genus on 
page 228. 


process of form branching from form. 


226 EVOLUTION FOR JOHN DOE 


Fhe most significant item in the chart is the line 
marked Lithistida, which is left unconnected. When 
the chart was prepared fifteen years ago, there was 
no way to determine whether this group was a 
‘‘grade’’ or an ‘‘order,’’ or whence it sprang. Instead 
of guessing about its origin the classifier indicated 
his ignorance. 

Another view of the sponges will show another 
truth that classification regularly reveals—the rela- 
tive largeness and smallness of the divisions. It is 
not entertaining; skip it if you don’t like the looks of 
it. For those who linger with it a minute I will ex- 
plain that the steps downward in subdivisions are 
shown, from greatest’ to smallest, by ‘‘One, I, 1, a’’— 
representing respectively sub-phylum, class, grade 
and order. The table shows only the large prelim- 
inary groupings, larger and more general than 
families, and far above genera. The size of type 
indicates, very imperfectly, somewhat of the relative 
number of families in each division. 


Sub-phylum One 
a. order 
b. order 


Sub-phylum Two 


J. Class 


1l;> Class 


a. order 
b. order 


TT Class 
1. Grade 


a. order 
b. order 
c order 


2. Grade (or this division may belong 
under Grade 1 as the d order) 


3. Grade 
a Order 


b. order 
IV. Class 


EVIDENCE FROM CLASSIFICATION 227 


We have seen the tree-like appearance of the 
largest divisions of a great phylum. If we should take 
the next step down in classification, and should chart, 
for example, the b order of one of the grades, we 
should produce just the same kind of diagram of 
branchings; the big bare limbs of orders would each 
have clumps of branches—the families. And each of 
these families would send out clumps of smaller 
branches—the genera. Each genus, if it was pros- 
perous, would fork into many twigs—the species. 
And each flourishing species would have several 
leaves—the varieties. And the leaves might be send- 
ing forth buds—some sub-varieties. 

The diagram on page 228 pictures one man’s class- 
ifying of a sub-genus of the big, black Eleodes beetles 
of the Southwest. This man would have been lost in 
the mazes if he had not known how to look for the 
course of development of each species and variety that 
he found. 

Suppose that you had encountered Mr. Blaisdell 
as he returned from his six-month collecting trip 
over the sage-brush plains and up the bouldery bar- 
rancas of the Mojave Desert, and suppose that you 
had asked him what a species is. Perhaps he would 
have sent you a copy of his bulletin, with this passage 
of the definitions marked: ‘‘Heterotype=an indi- 
vidual that forms an extreme of a specific or varietal 
series. Mesotypes=individuals connecting the ex- 
tremes of a series. Amphitypes=individuals that 
simulate another species. Monotype’’—and so on 
through polytype, sexitype, and others. So abso- 
lutely non-perfect were the species and varieties that 
they can not be conceived or in any way classified 
except by paying attention to that greatest truth of 
nature, that a species is a fluid form of life. 

Pause a minute to take stock of the labor that Mr. 


228 EVOLUTION FOR JOHN DOE 








Porc ie 
Obsoleta 2 
Knausii Omissa 
Carb i Pygmwa 





inn I 






Een 
Dewdisn Lustransa nthracina 
Quadricollis 
Cuneaticollis 
Humeralis 
Li X Pedinoides 
es. Rileyi / Neomexicana 
Ampla Carbon- Quadricollis /-—~ 


Tricosta 


ia LE Section Section 
cae 


Subgeneric Trunk 


Chart of one section of a genus of large, black beetles, 

after Blaisdell in the United States National Museum 

Bulletin 63. It shows the same sort of branching that 

is seen in the chart of the whole vast phylum of sponges 
on page 225. 


Blaisdell put into determining the twelve species and 
eight varieties of this one part of a genus of beetles. 
And his labor was only a portion of the whole; for six 
specialists had worked in the genus before him. Mul- 
tiply the total labor of these seven men by eight thou- 
sand, in order to know how much effort it took to 
classify all the beetles. Multiply the product by some 
large factor, in order to have the sum of expert toil 
that has been spent upon classifying all animals. 
Double the product, so as to include all the classifying 
of plants. Then—and not till then—you will appreci- 


EVIDENCE FROM CLASSIFICATION = 229 


ate slightly the amount of evidence that is furnished 
by classification. 

A classifier never can find a sharp line of demar- 
eation between different groups. Between most 
species there are varieties that bridge the gap; be- 
tween genera there are interlocking species; between 
families there are dove-tailing genera; to separate 
orders so clearly that no family will bridge the gap 
is usually impossible. Classification always indicates 
that if our knowledge could ever be complete we 
should see that there never had been any gap any- 
where, but that all transitions have been continuous, 
over bridges of variation that dropped out and dis- 
appeared from the record. ‘‘At this point,’’ we are 
told by botany, ‘‘the distinction between flowering 
and flowerless plants breaks down.’’ So deep a rift 
as that is well bridged over. The more men learn of 
fossil plants and animals, the more they are taught 
that in past times there have been bridges between 
forms that to-day seem wide asunder. Life has been 
a whole, and there has never been any such thing as a 
separate species that was not attached through its 
branching ancestry to every other form that ever 
lived and branched upward from the beginning of life. 
A modern classifier can no more conceive of a species 
without ancestry than a biologist can conceive of an 
animal that had no parent. 

I will close the chapter by a comment on the men 
who classify. So far as a rough count of the different 
sorts of sponges can be made, there are about two 
thousand five hundred species—only two thou- 
sand five hundred. It is well for us amateurs to 
try to stretch our imaginations to the classifying of 
the sixteen thousand species of spiders. Perhaps we 
had better excuse ourselves from trying to imagine 
the extent of the intricate labors of classifying the 


230 EVOLUTION FOR JOHN DOE 


sixty-one thousand species of mollusks. Even if we 
were willing to strain our minds to the breaking-point, 
we could not conceive the total of patient work that 
has gone to the making of a chart of all the animals 
or all the plants. Of this vast domain of classifica- 
tion no modern scholar can know thoroughly more than 
one corner. The botanists and zoologists are a great 
corps of tireless and clever campaigners against the 
mysteries of nature. No one can command them; 
there is no discipline. Some delve in coal mines for 
ancient ferns, some spend the years viewing grass- 
hopper eggs under a microscope, and others dredge 
the depths of ocean or thread the tropical forests or 
study agricultural pests at home. No horde of self- 
willed barbarians were ever so free to spread where 
they like and think what they choose. Yet they all 
think one way and—whether they will or not—contrib- 
ute to one fund of ever-increasing knowledge of one 
subject. Whenever they classify truly, they extend the 
kingdom of evolution. 


CHAPTER XV 
THE EVIDENCE FROM ARTIFICIAL SELECTION 


THE kind of evidence that comes from artificial 
selection has been outlined in Chapter IX—that is, 
the ways in which breeders select the variations pro- 
_ vided by nature through a series of generations, pil- 
ing them up as they occur in a desired direction, until 
they gradually develop a race that is widely different 
from the one with which they started. In this way 
many plants and animals have been slowly changed 
into forms so unlike their ancestors that they appear 
as different as a new species or even a new genus. 
Kixamples were given of two ways in which new va- 
rieties arise: (a) by selecting a series of slight varia- 
tions,* as in producing new kinds of pigeons or 
changing a small single daisy into a large double 
chrysanthemum; (b) by the sudden appearance of a 
new breed, as in the case of the hornless cattle or a 
new kind of peach. This sort of evidence has always 
been persuasive; it can be seen in operation; it indi- 
eates that all kinds of life, wild as well as cultivated, 
are variable and are prone to change to very different 
forms. 

There is no need here to add pages of further illus- 
tration, but there is need of showing in Part Two that 
the facts of artificial selection are an important kind 
of evidence for evolution. I will give a few examples 


*For variations that can not be cumulated see Chapter XXIV, 
Section ITI. 
231 


232 EVOLUTION FOR JOHN DOE 


which supplement Chapter IX, and will then explain 
why this line of evidence is, if taken by itself, incom- 
plete. 

Darwin founded much of his reasoning on his 
knowledge of the breeding of animals and plants. In- 
deed the evidence was so important to his theory that 
in 1868 he published two large volumes, The Varia- 
tion of Animals and Plants under Domestication, as 
a sort of ‘‘case-book’’ for the Origin of Species, a 
storehouse of evidence that was too bulky to go into 
the Origin. So exhaustive was this great collection of 
facts that it is still cited as the principal source of 
information about artificial selection. I give below 
five quotations from the book, which show how dif- 
ferences brought about by artificial selection may be 
very great, very firmly established, and sometimes 
fitted to succeed in wild life. 


1. The Japan pig is so distinct in appearance 
from all common pigs that it stretches one’s belief to 
the utmost to admit that it is simply a domestic va- 
riety. . . . The modification of the skull in the most 
highly cultivated races is wonderful. The whole of 
the exterior in all its parts has been altered: the hind- 
er surface, instead of sloping backwards, is directed 
forwards, entailing many changes in other parts; the 
front of the head is deeply concave; the orbits have 
a different shape; the canines of the upper jaw stand 
in front of those of the lower jaw, and this is a re- 
markable anomaly; the knobs at the base of the skull 
are so greatly changed in shape that no naturalist, 
seeing this important part of the skull by itself, would 
suppose that it belonged to the genus of pigs. 

2. The Niata cattle of South America have a fore- 
head that is very short and broad, with the nasal end 
of the skull curved upwards. The lower jaw projects 
beyond the upper. Even the connection of some of 
the bones is changed. Scarcely a single bone presents 


ARTIFICIAL SELECTION 233 


the same shape as that of the common ox, and the 
whole skull has a wonderfully different appearance. 

3. In the genus Auchenia there are four forms— 
the Guanaco and Vicufa, found wild and undoubtedly 
distinct species; the Llama and Alpaca, known only in 
a domesticated condition. These four animals appear 
so different that most naturalists, especially those 
who have studied these animals in their native coun- 
try, maintain that they are distinct species... . 
Now that we know that the domesticated species were 
systematically bred and selected many centuries ago, 
there is nothing surprising in the great amount of 
change which they have undergone. 

4, The humped cattle of India have run wild in 
certain parts of Oude and Rohileund, and can maintain 
themselves in a region infested by tigers. They have 
given rise to many races differing greatly in size, in 
the presence of one or two humps, in length of horns, 


and other respects. . . . There are magnificent wild 
bulls on the bleak Falkland Islands in the southern 
hemisphere. 


o. We must not overrate the amount of differ- 
ence between natural species and domestic races; the 
most experienced naturalists have often disputed 
whether the races are descended from one or from 
several aboriginal stocks, and this clearly shows that 
there is no palpable difference between species and 
races. 


The statement that ‘‘there is no palpable differ- 
ence’’ between the results of artificial selection and 
of natural selection may be misleading. For it is a 
fact that no artificial species has been produced which 
ean not breed with other species descended from the 
same stock; and that means that in the brief time of 
man’s selection no such deep and wide separation of 
types has been made as nature has created. Artificial 
selection is by no means a proof of natural selection; 
it is only an index to a strong probability. 


234: EVOLUTION FOR JOHN DOE 


Yet some of our domestic races are so ancient, as 
human history goes, and so thoroughly distinguished 
from any other forms existent in the world, that they 
seem to justify Darwin’s emphasis. No one has ever 
seen a wild llama; we know that it has been domesti- 
cated in Peru for four centuries and that it was prob- 
ably derived from the wild guanaco, but it exists now 
as a separate species. The Arabian camel has never 
been seen except as an animal domesticated by man. 
Our Indian corn has never been seen wild, and no an- 
cestry is known for it. The same is true of wheat. 
The differences between these results of artificial se- 
lection are certainly not ‘‘palpably different’’ from 
the species in nature. 

Certainly none of the hundreds of practical men 
who work in our agricultural colleges know how to tell 
the difference between artificial and natural species, 
nor are they much interested in the difference. They all 
work on the supposition that the variations and sports 
in nurseries are of the same kind as those that occur 
in nature, and that the new varieties they produce are 
not palpably different from what nature has produced 
through all the ages. If sports from buds of sugar- 
cane and potatoes are so important in artificial chang- 
ing of species, presumably the same sort of sporting 
has been a factor in nature’s evolution. If the Seneca 
cherry of 1923 sprang into existence with new quali- 
ties—ripening early and having a spicy flavor—pre- 
sumably such sporting seeds have had their share in 
causing nature’s results. When Pennsylvania State 
College gradually develops a tobacco leaf that has 
only half the ordinary percentage of nicotine, the ex- 
perimenters suppose that they are dealing with the 
same sort of mechanism which has caused tobacco and 
potatoes to branch from the common ancestry that 
every botanist knows about in nature. Of course the 


\ 


ARTIFICIAL SELECTION 230 


experimenters may be wrong; but thus far no one has 
made any progress in discovering a difference between 
their results and nature’s results. All men who collect 
and direct the variations of plants and animals sup- 
pose that their work is evidence for the Hvolution 
Theory. 

The strongest part of the evidence will bear re- 
statement in this chapter. If all artificial selection 
dealt only with domestic plants and animals, the evi- 
dence would be weak. The fact is that all artificial 
selection begins with a wild species. In recent years 
many experiments have been made with plants that 
were never domesticated, and it appears certain that, 
if an experimenter is patient enough and has enough 
time, he can always discover variations to work with. 
It is believed that every wild plant, and presumably 
every wild animal, could be developed gradually by 
artificial selection, into a form that is very unlike its 
present form. It would seem that artificial selection, 
however violent and abnormal it may be, is simply a 
use of the machinery of natural selection. Artificial 
selection may pull the wrong levers and may spoil the 
engine, but it indicates that the engine of natural se- 
lection is there. 


CHAPTER XVI 
THE EVIDENCE FROM THE STRUCTURES OF ANIMALS 


In tHe American Museum of Natural History 
there is a chart of the supposed course of development 
of animal life, from one-celled creatures to mammals. 
The makers of the chart would wish us to emphasize 
‘‘supposed’’ while we study the branching lines of 
their exhibit; for they know better than we how mazy 
and back-tracking the paths of evolution have some- 
times been and how puzzling is some of the scanty 
evidence. 

On the other hand, they would wish us to know 
that in many ways the evidence is copious and that it 
is extremely probable that their exhibit represents the 
main lines of evolution correctly. The principal parts 
of it were known fifty years ago, have been subjected 
to the severest criticism, and have stood the test. It 
is likely that the improved chart which can be made 
fifty years hence will differ only in some details. And 
the men who planned this diagram of life would wish 
us to understand something of the vast labor that has 
been necessary, by thousands of scientists in many de- 
partments, to secure the knowledge which made their 
chart possible. There is no guesswork in it. It rep- 
resents keen observation and close reasoning. 

The principal value of this graphie exhibit is to 
show us that the different sorts of animals do not 
have other sorts for ‘‘ancestors.’’ The worms, for 
example, which are placed higher in the chart than the 

236 





The chart in the American Museum which shows the course of evolution of 

animals, by the special kindness of Dr. F. A. Lucas. The lines do not indicate 

that animals ‘‘descended from’’ others, but that each sort branched from a 
common stem. Sec page 237. 


‘MoTTod ‘aITYM ‘YABP sS1O[O ody} FO ooURpIOYUT PoXttu ot} St 4st oyd VW 
‘ayIyM “YrVp :sxofoo Fo aed vB st 4yFop oyy FY ‘“dnois yovo Ut SUOTZBIOUS 991} SUTMOYS ‘S}BL UL OOUBPIIOYUL UBITOPUo IW 





STRUCTURES OF ANIMALS 237 


jelly-fish, are not ‘‘descended from’? jelly-fish. The 
fact seems to have been, as the chart shows, that the 
different forms of life have kept budding off into 
branches, which have divided into further branches. 
The squirrel, perched at the top, did not ‘‘descend 
from’’ some fishes that are below him; he is one of 
the latest twigs that come from a branch that came 
from a limb that grew from the common trunk. If 
human beings were to be placed in the chart, they 
could not be shown as descendants of any animals now 
living, but only as a twig from the ‘‘primate’’ limb of 
that common branch from which all mammals spring. 
All animals must have a common ancestry, but seldom 
is one kind known to have sprung from another kind. 
Though it is commonly said that birds developed from 
reptiles, it might be truer to say that birds and rep- 
tiles have descended from some common stock. 

The bottom of the trunk is labeled ‘‘Protozoa’’— 
that is, one-celled animals. Science does not know 
anything about the roots of this tree—the origin of 
life—and probably never will know anything. It does 
not know, with mathematical assurance, that the earli- 
est form of life was one-celled. But it finds all the 
evidence pointing in that direction and makes the sup- 
position until some contrary evidence appears. Sci- 
ence does not know positively that the first step of 
evolution was when two cells varied in such a way that 
they could live to better advantage in partnership; 
but science finds indications that such was probably 
the first step. Science supposes that, by a series of 
variations, many cells came to live in a partnership, 
forming a sort of colony. It is likely that these cells 
varied in diverse ways so that some became better 
adapted for obtaining food, some for digesting it, 
some for distributing it. When these several sorts 
of cells had become much differentiated, they were 


238 HVOLUTION FOR JOHN DOE 


no longer able to live separate lives; each sort was 
dependent on all the other sorts; and thus the earliest 
many-celled animals are supposed to have evolved. 

That sounds somewhat fanciful. Perhaps the idea 
would have remained a pure speculation if we had 
never known anything about sponges; but among these 
Wwe can see many stages of just such a process. There 
are sponges which seem to be mere colonies of similar 
and independent cells; other sponges in which the cells 
are highly differentiated and utterly dependent. In 
this case, as in every other part of the evolution chart, 
the biologists have not built upon their imaginations, 
but have always laid foundations upon facts now ob- 
servable in nature. 

Above the sponges the chart shows a branch of 
such salt-water animals as jelly-fish and sea-anemo- 
nes. At this point the needs of saving space and 
avoiding complexity have made the diagram mislead- 
ing; for the jelly-fish have continued to prosper ever 
since their ancient beginnings, and their line deserves 
to be extended to the same height where birds and 
frogs are displayed. A complete chart of evolution 
would show, from bottom to top, in what geologic 
period each type of animal arose, and would continue 
its line upward till it became extinct or reached the 
height of the present time. ‘This chart, more con- 
venient and graphic, indicates only how each type 
branched from the stem. 

Two main branches of many-celled animals are 
shown. The one at the right has ramified into a far 
greater number of types than the other—from several 
sorts of animalcules and mollusks to crabs, spiders, 
and insects. Most of these are small animals; but one, 
the giant squid, is large enough to give a whale a 
tough fight. 

At the base of the left branch are certain worms, 


STRUCTURES OF ANIMALS 239 


and just above these some ‘‘radiating’’ forms, like 
starfish. From here up all the types tend to a ‘‘ver- 
tebrate’’ form—that is, having a backbone. They did 
not descend from worms or starfish, but from the 
same parent stock that gave rise to worms and star- 
fish. So, as we look higher up, we are not informed 
that reptiles descended from fishes, but only that rep- 
tiles and fishes grew out of a common stem. 

it staggers imagination to see the results of ages 
of the evolution of structures put thus abruptly be- 
fore us in a disjointed series. We can not see how the 
gaps could be bridged. When we learn that the schol- 
ars themselves disagree about particulars, and that 
sometimes they imagine linking forms which they have 
never seen, we are excusable if we give a verdict of 
‘‘not proved. di 

Indeed such an exhibit of successive fe ices 
through a long development may misrepresent evolu- 
tion to us amateurs, for it implies that scientists have 
relied on a lot of clever conjectures. The truth is just 
the opposite. The unfilled spaces in the chart of 
evolution have always seemed more incredible to a 
biologist than they do to us. He knows how imitative 
nature always is and how the origin of a new bone is 
a prodigious work for her mechanism; he marvels at 
the ease with which college students can take it 
all on trust and repeat offhand, ‘‘Oh, yes, the leg 
evolved from a fin.’’ It is the scientist who sees that 
the gaps are extraordinarily hard to fill. It has 
always been the keenest scholar who has felt most 
dubious about the successive steps of the evolution 
of a limb or other organ. He has never accepted sur- 
mises and guesses. He has had to be convinced by 
an unanswerable array of facts. 

The study of structures is called anatomy, and the 
study of the similarities in the anatomy of different 


240 HVOLUTION FOR JOHN DOE 


animals is called comparative anatomy. The more 
science learns about comparative anatomy, the more 
it discovers those same continuous serves that are so 
striking in the geological record and in classification. 
The student of anatomy knows of finely graded forms 
from the limb of a lizard to the wing of a swallow, 
from the fin of a shark to the leg of a lion, from 
the smooth skin of a whale to the shaggy coat of a 
bear. The two ends of any such series of structures 
seem incredibly remote from each other. Every sci- 
entist of the nineteenth century, confronted with the 
extremes and asked to believe that one evolved from 
the other, was infinitely more skeptical than you and 
I can be; for he knew how distinct they are in the de- 
partments of nature’s workshop. Until he saw a dem- 
onstration of many actual steps in an anatomical 
series, he never credited the evolution of one from 
another. : 

Imagine that in 1855 Darwin had said to some 
young man who was beginning the study of zoology, 
‘“The hoof of a horse must have developed by gradual 
continuous stages from the fin of a fish.’’ Imagine 
the amazement of the young man. If he had lived 
till 1920, keeping himself abreast of the times and 
following each advance in zoology, he would slowly 
have learned—always against his will and his strong- 
est prejudice—that there is no escaping Darwin’s 
conclusion. It is now impossible for the comparative 
anatomist not to believe it. 

An outline of what the young man would have 
learned begins in the rocks. In the geological period 
before the coal began to form a lizard-like amphibian 
one day walked on the hard mud of a river delta 
where western Pennsylvania now is. His foot, about 
three inches long, was divided into two principal parts, 
but there was a bunchy third toe and a slight swelling 


STRUCTURES OF ANIMALS 241 


corresponding to a fourth toe. One of his tracks was 
covered in such a way that it was preserved while the 
mud was transformed to sandstone; and after Darwin 
died it was discovered by an American geologist and 
placed in the Yale museum. It is obviously the print 
of an amphibian’s foot, padded and creased and un- 
mistakable. It is the most ancient record ever dis- 
covered of any animal that went on feet. Above this 
stratum of rock there are, in all parts of the world, 
animals with five toes.* When these are classified 
in time order, they are found to branch into many 
kinds, which can be charted in different lines of de- 
scent. One line comes down unbroken to modern tur- 
tles, another to lizards and snakes, another to croco- 
diles. Two other lines can be traced to queer species 
that are all but extinct to-day, one of which is the duck- 
billed Ornithorhynchus of Australia. Many of the 
lines have completely died out. One developed into 
birds, and one into mammals. 

The young zoologist would have had small trouble 
in believing that all modern reptiles descended from 
ancient reptiles; a small part of the evidence would 
have convinced him completely. But birds! That 
would have been beyond belief for some years. Yet 
if he examined the structure of the winged reptiles 
that were found, and if he did not think that nature 
was making game of human beings, he would have had 
to believe that birds evolved from reptiles. The facts 
are patent in the museums of London and Berlin, 
where he could see animals the size of a crow that are 
as much like our feathered fliers as they are like the 
oldest lizards. Photographs can be faked, but these 
remais in the rocks can not be deceptive—unless 
Satan has played a practical joke on the geologists. 


*For the explanation of this great gap im the evolution of the 
foot see the next chapter. 


242 EVOLUTION FOR JOHN DOE 


The wing of the most ancient bird was, in part, a mem- 
brane stretched along the side of the body, like the 
gliding-planes of the extinct flying reptiles; and it 
was also like the true wing of a modern bird, sup- 
ported from the fore limbs and covered with feathers. 
Yet there were claws on the outer joint; and the head, 
skeleton and teeth were reptilian. No naturalist 
would have dared to imagine such a beast; nature made 
it and preserved two specimens for us to see. 

‘‘But what about the feathers?’’ the skeptic would 
have asked. ‘‘I can see that here really is a form 
midway between reptile and bird, but how could the 
scales change? You don’t show me any steps in the 
evolution of such an extraordinary structure as a 
feather. Am I asked to guess that in some vague way 
each scale grew longer and frayed itself out into tens 
of thousands of perfectly adapted barbules?’’ 

That is what he was asked to believe. Surely he 
might well have refused, since he had been taught to 
think of a seale as a fixed kind of structure, and of a 
feather as another kind of structure. But if we de- 
voted a year to the study of each, we should find that 
some fish have scales that are ‘‘like hair or feathers,’’* 
that the feathers of the cassowary are very simple 
structures compared with what we know as feathers, 
and that in young birds there is a coming and going 
of feathers such as we never see in any adult bird. 
We should learn that there is nowhere any hard-and- 
fast line to be drawn among all the forms that the cov- 
erings of vertebrates take: nails, skin, hoofs, scales, 
shells, plates, plumes, hair, down. We may go all the 
way along a series of structures from microscopic 
scales to the horny sections that make up a turtle-shell. 
Long famiharity with this blending of the different 


*Press report of William Beebe’s expedition to the Sargasso Sea, 
March 7, 1925. 


STRUCTURES OF ANIMALS 248 


structures that grow from the skins of animals would 
make it hard for any one to believe that they had sep- 
arate origins; for they seem all related and essentially 
similar. 

Thus the young zoologist would have grown to 
believe that undoubtedly birds evolved from reptiles. 
Not that the few indications here given would teach 
him—far from it—but that in his studious life he 
would encounter the hundreds of similar links in the 
chains of evidence that scientists are forever discov- 
ering. Bare logic would not be effective; a few dozen 
probabilities would not persuade him. But the multi- 
plied examples as the years went by would create an 
unshakable conviction. 

As for the descent of mammals from reptiles, it is 
just a repetition of similar evidence from many series 
of structures: the order of the fossils and the rare 
animals still surviving in some corners of the earth 
give an indication that is irresistible. A student of 
comparative anatomy learns that there is no hard-and- 
fast line between reptiles and mammals—not even 
among the animals that now live. Perhaps to me in 
my ignorance there seems to be an unbridgeable dif- 
ference between laying eggs and bringing forth young 
alive. But the biologist knows of a gradation from one 
kind of bearing young to the other kind: an egg may 
be hatched outside of the body, or it may remain with- 
in the mother till it is hatched, or it may remain at- 
tached to the mother till 1t has partly developed. 
Some fishes and snakes bring forth their young alive. 
The biologist gives the same name to the egg of a 
snake and to the egg of a sparrow and to the egg of 
a rabbit; he can not distinguish sharply between the 
different kinds; he can not conceive that they come 
from different sources; all his evidence shows that 
each mode of bearing young was developed from some 
preceding mode. 


244. EVOLUTION FOR JOHN DOE 


The early mammals were small. Apparently they 
developed in many races through long ages, picking 
a living as best they could by keeping out of the way 
of the huge reptiles that dominated the life of the 
world. If our zoologist kept pace with the fossil dis- 
coveries, he might have been convinced of this before 
1880. But if any of his early doubts then remained 
he might have said, ‘‘It is too much to ask me to sup- 
pose that from a five-toed animal a few inches high 
there should develop an animal five feet high that 
walks on a solid hoof. There is no evidence for such 
profound alterations.’’ Yet most geologists of that 
time believed that such had been the history of the 
horse, and they confidently expected that the proof 
would some day come out of the rocks. It came. There 
was a find of a small three-toed horse; and another 
that was smaller, with the side toes longer; and an- 
other that was smaller still. One day the news flashed 
over the wires that a four-toed horse a foot high had 
been found. Now a series of horses has been set up 
in a museum,” showing graphically the actual prog- 
ress of teeth and limbs as they changed and enlarged 
and took different proportions, from little twelve-inch 
Eohippus to a racing thoroughbred. Similar series 
are now known for camels and elephants. 

The experience of this one zoologist represents 
the course of scientific opinion since 1860. Then evo- 
lution was seen at once to be a shrewd and likely hy- 
pothesis, but the gaps in the series of structures were 
so many and so great that few geologists could expect 
them to be accurately filled. Every decade has made 
some remarkable contribution to the evidence, and this 
steady accumulation which has always fulfilled proph- 

*The original series, which Huxley viewed with so much delight, 


re sores for the Peabody Museum at Yale by Professor O. Q, 
arsh. 


STRUCTURES OF ANIMALS 245 


ecies and never disappointed them, has converted the 
hypothesis into an axiom of zoology. 

You may be wondering why a chapter on structure 
keeps talking about the geologic record. ‘‘Why,’’ you 
ask, ‘‘must geology and anatomy be mingled in this 
way?’’ The answer is that the subjects are insep- 
arable, as can be illustrated from the life of Huxley. 
He took a medical degree at the age of twenty, studied 
marine zoology till he was twenty-five, and at the age 
of twenty-seven, when he first met Darwin, had 
small faith in evolution. To him, as a student of 
structures, the gaps between the different classes of 
animals were too great to be bridged by any theory 
of common descent. He believed that even species 
were unchangeable forms of life. If he had never en- 
countered any evidence outside his own field, it is 
probable that he never would have accepted Darwin’s 
theory. But the fossil record was pointed out to him, 
and then he realized that the most incredible links of 
succession were actually to be seen in nature’s mu- 
seum. His judgment of structures had to yield to 
the knowledge that paleontology put before him. 
When he based his anatomy on these facts, he found 
that baffling mysteries were cleared up, and that his 
study of structures could safely be built on the new 
foundation. And this, mind you, was long before the 
discovery of the reptile-like bird or the series of 
fossil horses. Huxley expressed his debt to geology 
thus: ‘‘The primary and direct evidence in favor of 
evolution can be furnished only by the fossil record.’’ 

I suspect that even the combination of paleontology 
and anatomy would not have been absolutely convinc- 
ing to the young zoologist whose career we have been 
tracing. I can guess that, if he was at all like me, he 
would not have surrendered till he had learned of the 
entirely different line of evidence that is explained in 


246 HVOLUTION FOR JOHN DOE 


the next chapter. The structures of animals, taken 
by themselves, might not have seemed a proof; they 
link together and complete the evidence that is in the 
rocks and the evidence that is in embryos. As you 
read the rest of this chapter about structures, bear in 
mind that it is going to be supplemented in an extra- 
ordinary way. 

Consider one of the simplest cases of evidence from 


structure. If we make a list of all the animals that — 


have five digits at the ends of their limbs, we have 
reason to suspect that they are all related. The way 
those five fingers or five toes appear in so many 
guises among the vertebrates, but nowhere else in the 
animal kingdom, is remarkable. How could it happen 
—as a set of unrelated accidents—that a panther and 
a mouse and a frog should have their feet built on the 
same five-toed plan? The front limb of a bat looks 
like a five-fingered hand with enormously long bones, 
one of which extends beyond the wing as a claw. A 
seal has no apparent use for bones in its flipper—for 
fish swim faster with no bones in their fins, and seven 
bones or seventeen bones would make as good a frame 
for a flipper. But, no—the seal has the same five 
fingers. The structure of a whale’s fin is utterly 
unlike that of any fish; it is an arm—for there is a 
big bone at the top, then a pair of bones, then a wrist, 
and then five digits, one of which is shorter, like a 
thumb. It can hardly be an accident that so many 
backboned animals have at the ends of their limbs a 
hand-like structure—no matter whether they live on 
land or sea—while no other phylum of animals has 
anything of the sort in its anatomy. 

If this five-finger structure is studied, it is found 
to be wonderfully prevalent, though in all sorts of 
disguises and concealments. In the wing of a bird, 
though the limb structure has been modified almost 


‘OFZ 90Rq “MOTJIMGODAL PUOKS JSOW[B poaytpowu wseq SBY aInjont}s Sty spitq FO SoUIM OY} UT * * * ‘s}PUOUTTBIDTOD 
PUB SASINOSIP JO $}LOS [[B UL Yonoyy “yuoTBaAoid AT[NJLapUOM oq OF PUNOF St Yt ‘potpNys st aiNjon.tys AVvsuy-9AY oy} FY] 





é 
a 
B 
J 
_ 
f 
: 


me 
or ae 
9 iY ine we 
SaG 


WE e, 











The five-finger structure in the wing of a fruit-bat, above. Compare this modern 
apparatus with one of the earliest of Nature’s efforts to make a wing. From 
Seeley’s Dragons of the Air. 





STRUCTURES OF ANIMALS 247 


beyond recognition, there still remain three little bones 
of the five of the original foot; and a rudimentary 
fourth one has been seen in embryos. In the bird’s 
foot there are three prominent bones (the ‘‘metatar- 
sals’’), one small one, and the stunted remnant of a 
fifth. | 

Here we have opened up a whole new realm of 
structure. We wonder to what extent these remnants 
of bones could be found elsewhere among the ver- 
tebrates. They are a regular element of anatomy; so 
that if we know how to detect them, we can add vastly 
to the number of five-fingered animals. In fact the 
student comes to feel that any number smaller than 
five is abnormal and must be the result of a loss at 
some time in the history of any modern species. He 
calls these undeveloped parts ‘‘vestigial,’’? for they 
are vestiges or slight remains of what was once full- 
grown. 

A whale is an exhibit of many remnants of struc- 
tures that are of no use whatever to it, though they 
are highly important to the land-living mammals in 
which they are fully developed. Buried in the body 
of some species of whales, detached from the backbone, 
floating in the flesh, are some small remains of legs. 
They are at the point where a pair of hind paddles 
would naturally be. And in some snakes the same 
vestiges of legs appear. Jn the seal’s body the cor- 
responding bones have a strong development—into a 
regular leg-like series of thigh, lower leg, ankle, foot, 
and toes—to form the frame of the hind paddle. The 
only vestiges of hair on a whale are a few bristles near 
the mouth; the fur seal has the finest coat of hair in 
nature. The bones of the head of a whale are not the 
bones of a fish, but strictly those of the land-dwelling 
mammals; the skull of a seal is still nearer to the land- 
dwelling type. One kind of whale has true mammalian 


248 HVOLUTION FOR JOHN DOE 


teeth, but so vestigial that they never come through 
the gum; the seal’s teeth are strong and useful. 

An ingenious naturalist who speculated on seals 
and whales could note that a seal, which spends much 
of its time on the land, is more land-like in structure 
(as shown in a dozen ways other than the hind limbs 
and teeth and eyes and ears), though it has much of 
the fish-like form. He could note that a whale, which 
never lives on the land, has almost entirely a fish-like 
appearance. Then he could hazard a guess that in 
some past age certain four-footed mammals found 
good hunting in the ocean, that every slight variation 
in structure which fitted them to move better in the 
water and to stay in it longer was useful and was se- 
lected to survive, and that thus there was a gradual 
adaptation to sea life. He could guess that the seals 
had gone one-fourth of the way toward complete sea 
life, and the whales about ninety per cent.—for the 
whales must still come to the surface to breathe air. 
If such a supposition about structures stood all alone 
in the world, it would be no more than a probability 
till other series of structures had been studied. 

Some wings form such a series. It begins with 


squirrels which can make longer leaps because they — 
are helped by an expanse of skin stretched along the — 


body and held out as a gliding-plane between the legs. 
Many animals of very different kinds—from squirrels 
to fish—are helped in their motion by a similar device. 


Such a membrane is most completely developed among — 
the bats, where it is supported on the excessively long — 
fingers and is like a webbed hand. The extreme of — 
the series is the feathered wing stretched along the © 
whole arm. Other wings form a series that is an en- © 
tirely different piece of architecture—a membrane ~ 


supported on extended ribs. A third type of architec- 


ture is the wing of all the insects, which is not sup- _ 


f 
{ 





STRUCTURES OF ANIMALS 249 


ported on limbs, but is an entirely different kind of 
outgrowth from a different element of the body. 

When all the wings of animals are thus assorted 
into three groups of structure, it appears that the 
second is rarely seen. The first is the one that has 
been developed in two lines: the feathered arm-wing 
of the birds, the hand-and-leg membrane of the bats. 
The third has branched in the most extraordinary and 
successful ways among the wasps and flies and moths 
and bugs. Each type of wing shows a series. Each 
type of structure appears, when all are charted, to be 
a well-defined pattern which goes off at an angle from 
the other types. As we trace them back in time, we 
can see the similarity of their origins—that is, as 
outgrowths of the body-covering that were somewhat 
useful for aiding motion. We can see how each sort 
radiated farther from the other sorts in the course of 
ages, like the spokes of a wheel. But we never dis- 
cover, in wings or in any part of anatomy, that the 
lines ever come together again. 

If all the structures for seeing are classified and 
charted, they fall into three distinct types: the eyes 
of vertebrates; the eyes of mollusks; the eyes of in- 
sects. The first type of structure is found among 
all fishes and reptiles and mammals; every form is 
only a slight variation of the one architectural type. 
Nothing like the first type is ever found in insects or 
erabs or lobsters; nothing of the third type is ever to 
be seen in squids or snails. It appears that eyes, like 
wings, can be arranged in lines of structure that had 
similar origins—that is, in spots of the body that were 
sensitive to hight. We can see how each type passed 
through a series of changes in a long course of devel- 
opment. 

This fact of series of structures is observed in every 
phase of animal life. An armored snail and a pulpy 
slug appear unlike and unrelated; but the student 


250 HVOLUTION FOR JOHN DOH 


finds an unbroken series between the two extremes, 
through smaller and smaller shells, to a mere vestige, 
to a rudiment under the skin, to no trace at all. The 
heart of an ox is unlike the heart of a shark; yet, 
though they are such different structures now, we 
must suppose that there is a line of descent to a com- 
mon origin. So we could fill page after page—and 
great volumes have been filled—with these examples 
of the series that comparative anatomy has discov- 
ered. A dozen series would prove nothing; a hundred 
would make us suspect; a thousand would suggest a 
strong probability. When the students of anatomy 
find that in every respect the structures of all animals 
are always arranged in such ways that they could have 
been developed by inheriting variations, they feel al- 
most persuaded. After they have searched a hundred 
years for some other reasonable explanation of the 
structures and have found none, then they are con- 
vineced. 

The whole study of structures fits in with the 
results of classification. An example is the eye of a 
hawk and the eye of an octopus. These animals had 
to be classified in entirely different phyla—that is, in 
the most widely separated groups, profoundly unlike 
in organization. Yet their eyes were remarkably 
similar: each had cornea and lens and retina. This 
was perplexing; it seemed as if the evidence from 
structure was at odds with the evidence from classifi- 
eation, and the early skeptics about evolution made 
much of the argument. But their own reasoning 
proved that they were wrong: the eye of an octopus, 
for all its similarity in appearance, is built by a dif- 
ferent portion of the body, and is, in its origin, very 
different from the hawk’s eye. As in this case, so 
in all others: the two kinds of evidence never have 
failed to support each other. The evidences of struc- 





STRUCTURES OF ANIMALS 251 


ture have never been made doubtful by the facts of 
the fossil record, but have in the most complete manner 
always been vindicated by the fossils. The three kinds 
of evidence, which are quite independent of each other, 
check perfectly. . 

The evidence from structure is the kind that is 
least understood by general readers. The ordinary 
way of thinking about evolution is shown im the ques- 
tion, ‘‘How could a snake be changed into a turkey?”’ 
Each of these animals is at the end of an extremely 
long line of development. It is like a topmost twig 
of a branch on which some lower limbs have died and 
some have branched into varied forms. The evolu- 
tion of forms never leaps across from the end of one 
twig to the end of another. Evolution is always a 
branching from below. If the student of structure 
follows back, down the tree of life, from the twig of 
snakes, he will come to a certain reptile stock; and if 
he follows down from the twig of turkeys through the 
branch of modern birds to the limb of ancient birds, 
he will come to the reptile stock that gave rise to 
snakes. He does not want to do this; he has no ‘‘will 
to believe’? it; he knows full well that many a part of 
the tree of life is undiscovered. But when he is 
thoroughly acquainted with all the lines of develop- 
ment of structure—from the short and obvious ones 
to the far-reaching and baffling ones—he has no option 
but to believe that every species of animal which ex- 
ists came originally from a common ancestry in a very 
simple form of life. 

Or perhaps it would be more correct to say that 
he suspends judgment until he learns about the evi- 
dence that is seen in the development of eggs, and then 
has no option but to believe. 


CHAPTER XVII 
THE EVIDENCE FROM EMBRYOS 


A criticaL reader of the previous chapter may have 
noticed one point at which I seemed to slip hastily over 
a dubious description—the account of the earliest fos- 
sil footprint: ‘‘His foot was divided into two prin- 
cipal parts, but there was a bunchy third toe and a 
slight swelling corresponding to a fourth toe.’’? The 
description passed quickly on to the five-toed reptiles, 
and then to the wide development of the five-toed 
foot among mammals. Thus it implied that reptilian 
feet were evolved through a three-toed and a four-toed 
form. No evidence was offered of any knowledge 
that this actually was the course of evolution. 

No evidence could be offered in the previous chap- 
ter, because none has been found in the rocks. Yet 
no student of fossils doubts that there was such a 
course of evolution. If he had nothing to rely on 
outside of his own field, he would be assured. But he 
has, from an entirely different source, a confirmation 
of a most impressive sort. It is a form of evidence 
that clinches all the other probabilities so completely 
as to seem almost uncanny when any person first 
hears of it. It is furnished by the microscope, from 
observations of what takes place in eggs while they 
are hatching. 

If you could look through a biologist’s microscope 
at the developing egg of a mud-puppy (alittle, smooth- 
skinned, lizard-like salamander), this is what you 

252 


THE EVIDENCE FROM EMBRYOS — 2538 


would see. The single cell divides into two; each of 
these two divides into two others; and the process con- 
tinues until there is a globule composed of a great num- 
ber of cells. Inits next stage the egg becomes a hollow 
globe. During the third stage one half of this globe 
bends inward, while the other extends itself around 
the bent-in part, and there results another globe 
with an inner and an outer layer. Now the embryo 
seems to be really under way. What follows 
has been described by Huxley in words of almost po- 
etic enthusiasm: ‘‘The plastic matter undergoes 
changes so rapid, and yet so steady and purpose-like 
in their succession, that one can only compare them to 
those operated by a skilled modeler upon a formless 
lump of clay. As with an invisible trowel, the mass is 
divided and subdivided into smaller and smaller por- 
tions, until it is reduced to an aggregation of granules 
not too large to build the finest fabrics of the organ- 
ism. And then it is as if a delicate finger traced out 
the line to be occupied by the spinal column, and 
moulded the contour of the body, pinching up the 
head at one end, the tail at the other, and fashioning 
flank and limb into due salamandrine proportions, in 
so artistic a way that, after watching the process 
hour by hour, one is almost involuntarily possessed 
by the notion that some more subtle aid to vision than 
a lens would show the hidden artist, with his plan be- 
fore him, striving with skilful manipulation to perfect 
his work.’’ 

The embryo that Huxley described has at first 
only one toe. After a few hours this has swelled and 
shows three slight protuberances. These grow stead- 
ily more distinct, until the one at the end and the one 
at the right look almost like pulpy toes. Now the 
third toe (the one at the left) protrudes more and 
more, and later there is at its lower left side a fourth 


954 EVOLUTION FOR JOHN DOE 


swelling; this becomes a well-extended fourth toe. 
Finally from the lower left side of this fourth toe 
grows the fifth stubby toe. By this time the second 
and third ones have doubled their length, and there is 
your salamander foot with its five digits.* The steps 
that were conjectured from the order of the fossils 
are here visibly reproduced in nature’s moving pic- 
ture, the development of an egg. A record in the 
rocks, which extended over millions of years of slow 
evolution from species to species, is here rehearsedt 
before our astonished eyes in a few hours. It is as 
hard to believe that the two records are not related 
as it would be to believe that the White House and a 
photograph of it were accidental similarities. 

What was conjectured about the evolution of the 
parts of animals, as this was judged simply from the 
comparison of their structures, can be seen as the 
minutes go by while we gaze at the building of a body 
in an egg. It was hard to see how an extra toe could 
‘Just somehow sprout’’ from a three-toed foot; and, 
indeed, we may never know how it could. Yet in the 
making of every individual salamander the fourth 
toe, and then the fifth toe, do sprout. The fact of 
millions of years of evolution of a race is written for 
our skeptical eyes whenever we watch the ‘‘inyisible 
trowel’’ form a foot in an embryo. 

More difficult still is it to imagine how in the evo- 
lution of such a complicated creature as a lobster the 
claws and feelers and legs were ever derived from a 


*Description after Lull, from Rabl. 

tThis ‘‘recapitulation theory’’ was much overworked previous to 
1910, and was extended with enthusiasm to help in the harder parts 
of classifying. Hence some distrust of it arose. This was put very 
strongly in the old Britannica article by Driesch, and echoes of the 
caution are heard in recent texts. ‘‘But,’’ says Professor W. B. Scott, 
‘none of the criticisms denies, and many strongly affirm that em-: 
bryology affords some of the strongest and most convincing evidence 
in favor of the evolutionary theory.’’ 


THE EVIDENCE FROM EMBRYOS — 255 


set of those simple and similar segments into which 
the primitive body of its ancestors was divided. Per- 
haps we shall never learn how. The fact that there 
must have been such evolution through long ages is 
brought home to the observer of the shaping of any 
embryo lobster. Let Huxley tell in his vivacious 
style what he once saw under his microscope: 


Our lobster has not always been what we see it; 
it was once an egg, a semi-fluid mass of yolk, not so 
big as a pin’s head, contained in a transparent mem- 
brane, and exhibiting not the least trace of any one 
of those organs whose multiplicity and complexity in 
the adult are so surprising. After a time a delicate 
patch of cellular membrane appeared upon one face 
of this yolk, and that patch was the foundation of the 
whole creature, the clay out of which it would be 
molded. Gradually investing the yolk, it became 
subdivided into segments, the forerunners of the 
rings of the body. Upon the surface of each of the 
rings thus sketched out a pair of bud-like prominences 
made their appearance—the rudiments of the appen- 
dages of the ring. At first all the appendages were 
alike, but, as they grew, most of them became distin- 
guished into a stem and two terminal divisions, to 
which, in the middle part of the body, was added a 
third outer division; and it was only at a later period 
that, by modification, the limbs acquired their perfect 
form. 

Thus the study of development proves that the 
doctrine of unity of plan is not merely a fancy, that 
it is not merely one way of looking at the matter, but 
that it is the expression of deep-seated natural facts. 
The legs and jaws of the lobster may not merely be 
regarded as modification of a common type; in fact 
and in nature they are so, the leg and the jaw of the 
young animal being at first indistinguishable. 

These are wonderful truths, the more so because 
the zoologist finds them to be of universal applica- 


206 HVOLUTION FOR JOHN DOE 


tion. The investigation of a polyp, of a snail, of a 
fish, of a horse, or of a man, would have led us to 
exactly the same point. Unity of plan everywhere lies 
hidden under the mask of diversity of structure—the 
complex is everywhere evolved out of the simple. 
Every animal has at first the form of an egg, and 
every animal and every organic part, in reaching its 
adult state, passes through conditions common to 
other animals and other adult parts. 


It is impossible for Huxley, or for any man of 
mental keenness, to remain scientifically prosy when 
he states the fact that ‘‘every animal and every part 
passes through conditions common to other animals 
and other adult parts.’’ No creature, in its early 
stages, has the outward look of its species—no, not 
even of its great class or sub-kingdom of animals; it 
is, so far as human eyes can see, at first a single cell, 
then a colony of cells, then a folded creature within 
an inner and an outer layer. It is true, in a very gen- 
eral way, that the embryo of every animal progresses 
up the scale of lower phyla to that point of advance 
where its limit lies; it emerges from the embryo to be 
a lobster, or to be a fish, or a reptile, or a bird. 

It would appear as if nature could not originate 
any novel way of bringing an animal to maturity, but 
always had to follow the ancient process that she 
learned with great slowness in the course of long 
ages, while the higher races very slowly evolved. 
What she learned to do in the early eras of life she 
can now do with rapid ease, so that the lowest stage 
of any embryo is gone through with in comparatively 
short time; and as the limit of development of any 
embryo is reached, its processes take longer. It 
would seem, if we continue this comparison with an 
artisan, that nature has learned many short cuts in 
the steps that took her so long while she fashioned 


THE EVIDENCE FROM EMBRYOS ~— 257 


the changing races. At any rate, our eyes can not see 
all the steps as we observe a developing egg. The 
early ones seem hurried and huddled together; there 
seem to be quick jumps over gaps; and there are com- 
binations of processes that probably never were in 
adults, but have been invented for use in embryos. 
Hence the history of all ancestors is not told fully 
and clearly in the egg. What can be seen, especially 
of the older parts of the line of descent, is a distorted 
and transformed history. But a history itis. Many 
of the chronicles of descent are there under some 
guise or other. The development of every individual 
is a partial and blurred ‘‘repetition’’ or ‘‘recapitula- 
tion’? of the long development of the race. Hence 
the facts of the development of embryos are ex- 
pressed by the name ‘‘Recapitulation Theory.’’ 

What happens when a hen sits on her eggs, as 
every encyclopedia now tells us, is this: a fish-like 
animal appears, with gills and a long tail; then legs 
bud at four points, and there is a lizard-like animal; 
the fore legs develop rapidly into wings; the hind 
legs become chicken legs. The record of tens of mil- 
lions of years in the rocks is rehearsed here in three 
weeks. When the ovum of a pig begins to develop, it 
is hardly to be distinguished from the early stage of 
a chick, for it looks like a fish; then its legs bud—not 
pig’s legs in appearance, with a cloven hoof, but legs 
that resemble a lizard’s; the fore limbs and the hind 
limbs develop into pig’s legs. The embryo of a rab- 
bit seems to be a fish and a reptile before it becomes 
a rabbit. Every mammal, in its own life, lives rap- 
idly through the stages that cover such stupendous 
ages in the rocks. If John Doe is curious about his 
own evolution, he should read an encyclopedia article 
that describes the stages through which he himself 
lived during the first months of his life. 


258 EVOLUTION FOR JOHN DOE 


The revelation of race history that comes from 
embryos is of a kind that rivets attention. It is 
startling and romantic to the last degree. The nature 
of it may be put into graphic form thus: An English 
surveyor goes tapping about the hills with his ham- 
mer, never dreaming of evolution, and as he pieces 
together the facts in the rocks they spell out before 
his astonished eyes a history of an order in which 
animals succeeded one another while the different 
rocks were formed. In a laboratory of northeastern 
Prussia a Russian scholar works month after month 
with his microscope; through the lenses there swims 
into his ken, as the egg develops, the history of the 
same order of succession. The testimony of the 
rocks and the revelation from the egg coincide. 

Long before the Origin of Species appeared, the 
embryologists had seen the stages of development in 
eggs. One of the greatest of them used to exclaim 
as he showed his specimens, ‘‘I have here the embryos 
of lizards and pigs and rabbits, but I can not tell 
which is which. They are all alike.’’ Until 1859 there 
was no meaning to these facts. Then embryology 
took a fresh start, and it began to contribute to 
evolution. : 

The first actual demonstration that embryos and 
rocks tell the same truth was not made until 1869. In 
that year a German named Waagen published his 
observations of three species of coiled ammonite 
sfells—the kind that Holmes addresses in his Cham- 
bered Nautilus, Waagen found in three successive 
strata the three species arranged, of course, in the 
order of their evolution. Many of the specimens were 
of half-grown shells, and of shells only in infancy. A 
study of some of the ufideveloped shells in the top 
stratum showed that they resembled the mature 
shells of the earlier species in the stratum next be-« 


THE EVIDENCE FROM EMBRYOS = 259 


low; and a study of shells still less developed proved 
that they resembled the oldest species in the lowest 
stratum. Nature had arranged in this series of rocks 
a display of embryology, a demonstration that every 
shell in its individual life had gone through just the 
changes that the race of shells had gone through in 
the three strata. No more precise or sensational sort 
of proof was ever known to science. 

The life histories of all sorts of animals have 
been studied with most painstaking scrutiny. There 
have been able embryologists who would have given 
all they owned to prove that the development of an 
egg does not parallel the fossil record, and they have 
argued and protested with vehemence. So startling 
a correspondence between two such different depart- 
ments of science is unique, and the reasoning about it 
has been subjected to a long and fierce test. The 
recapitulation theory has stood the test. No evidence 
from the microscope collides with any evidence from 
the fossils. In many striking and conclusive ways 
the microscope has shown zoologists how to classify; 
but it has never given evidence counter to the prin- 
ciples of classification. If the combination of the fos- 
sils and the embryos is not a proof, then the universe 
is a whirligig and man’s reason signifies nothing. 

It may perhaps be conceivable by some minds 
that the records of rocks and eggs merely happen to 
have a resemblance. Possibly some intellects can 
suppose that all nature was planned as a temptation, 
to deceive the minds of scientists by a coincidence 
that means nothing. We can not prove that a Creator 
might not have paralleled the embryos and rocks in a 
fit of humor, Evolution can not be demonstrated. 
But every modern scientist, aware of how serious and 
uniform nature always is, must reject any such eva- 
sion of evidence. There is nothing for any logical 
mind to do but to accept the Evolution Theory. 


CHAPTER XVIII 
THE EVIDENCE FROM BLOOD 


Tue chapter on the structures of animals was lim- 
ited to the large and noticeable features of the body, 
such as bones and organs. It could have been ex- 
tended to all the minute portions, like the fluids and 
cells that carry on the life processes. For just as na- 
ture follows one architectural pattern for limbs and 
eyes in each sub-kingdom of animals, so for each 
small matter of physiology she keeps to a general 
similarity throughout the whole of a group. Take 
the blood as an example. We should suppose that the 
warm blood of a bird was more like the warm blood 
of a mammal than the cold blood of a turtle. But this 
is not so. For birds are of the reptile stock, and 
every corpuscle that carries oxygen to their tissues 
is made on a reptilian pattern—that is, it has a nu- 
cleus, and is a true cell. The full-grown red corpuscle 
in a mammal’s blood has no nucleus. Hence a biol- 
ogist could tell by a glance through his microscope 
whether a sample of fresh blood came from a lower 
vertebrate or a mammal. 

The differences in the blood extend to very 
much finer matters than corpuscles. The chemical 
components are different. And they do not differ 
erratically, independently, but always in correspond- 
ence with the general structure of the phylum and 
class and order and family... If we had instruments 
fine enough to detect all these slight and orderly dif- 

260 : 


THE EVIDENCE FROM BLOOD 261 


ferences there is no doubt that a mere examination 
of a specimen of blood would show from what genus 
it came, and from what species. Every particle of 
blood is compounded by the recipe that fits its par- 
ticular species, a recipe that is unlike the formula for 
any other species. These distinct and precise differ- 
ences that must be in bloods was somewhat under- 
stood forty years ago. In 1904 an elaborate treatise 
on the subject was published in England, called Blood 
Immunity and Blood Relationship, which explained a 
most accurate and far-reaching method in physiology. 

The knowledge of blood relationships has fur- 
nished the latest kind of evidence for the detectives 
who seek the clues to evolution. It is evidence from 
an unexpected source, entirely independent of any 
knowledge that comes from other lines of research. 
The nature of these ‘‘blood tests’? and of what they 
show may be briefly outlined as follows: 

If some serum of the coagulated blood of a horse 
is injected into the veins of a rabbit, the rabbit’s 
blood forms a sort of anti-toxin against the chemicals 
of the invading serum from the horse. If, now, some 
serum from such prepared rabbit blood is put into a 
solution with horse blood, there is a chemical reaction 
that is well known and unmistakable. But if the pre- 
pared rabbit blood is put with ordinary rabbit blood, 
there is no reaction. In other words, the blood that 
has bred anti-toxin against the horse serum is a very 
sure and delicate test for horse blood. The evidence, 
it should be noted well, is not from living cells or tis- 
sues or any form of life: it is from a very different 
source—from the field of chemical reaction. 

The test works so perfectly for human blood’ that 

*In Science for May 8, 1925, is an article by Landsteiner and Mil- 


ler, of the Rockefeller institute, "confirming and extending the Nuttall 
tests in a remarkable way. 


262 EVOLUTION FOR JOHN DOE 


it can safely be used in murder trials to determine 
whether or not a stain was made by blood from human 
veins. It indicates in a very detailed way that the re- 
lationship of man to other animals is what the evi- 
dence of anatomy and the embryo shows. 

A long series of experiments has been made with 
all sorts of combinations; the result is that ‘‘anti- 
blood tests’’ are found to be of varying intensity. 
For example: the rabbit’s blood that is ‘‘anti-horse’’ 
will react against the blood of a mule or a zebra, but 
less strongly; it will react less strongly still against 
the blood of a cow or a pig. It is found to be gener- 
ally true that in proportion as any animal is more’ 
nearly related to the horse in classification its blood 
gives a stronger reaction, and that as the relation- 
ships of different animals grow more and more dis- 
tant from the horse the reactions from their bloods 
grow weaker and weaker. The chemical evidence is 
in close correspondence with the evidence from classi- 
fication and structure. 

In fact the anti-blood tests are now well enough 
understood and tabulated to be used as evidence in 
clearing up some doubtful points of classification. 
Anti-pig serum,for instance, will act strongly against 
the blood of any member of the pig family; it will 
act much less strongly against the blood of camels and 
llamas (about equally for these nearly-related ani- 
mals); and much less still for a whale. 

Blood tests have shown that birds are more nearly 
related to turtles than they are to lizards, and thus 
confirm in a most curious way what the experts in 
fossils had conjectured. 

How to classify the horse-shoe crab has always 
been a puzzle. The study of embryos showed that it 
was more nearly related to the scorpions than to real 
crabs—an unexpected verdict. Hence the blood-test 


THE EVIDENCE FROM BLOOD 263 


men must have felt some excitement when they had 
perfected their art enough to apply it to this peculiar 
puzzle. The blood test confirmed the embryos. 

What fame would have come to these workers with 
serums if they could have produced evidence against 
the rocks or the embryos! Their experiments would 
have been proclaimed in every scientific journal, and 
the newspapers would have written them up. They 
eould have sold one hundred thousand copies of a 
book entitled Darwin Overthrown by Blood. But 
there was no such fame or wealth in store for them. 
They could do no more than add to the list of evi- 
dences which always grow stronger, never infringe 
on one another, and multiply one another’s strength. 
EKivery one who has ever learned something new about 
the life of plants and animals has always—whether 
he would or not—brought fresh witness to the [vo- 
lution Theory. 


Yad 
Mehta N 





PART THREE 


Tue History or Evoitution 


tik ee 
AS 
ta) 


v, s ; 


LOU tH! , 
A RRS 


Ne 


fet Mille ay ah 
aCe He aA, 
0 Vinee 
ay aed, 





CHAPTER XIX 
LAMARCK 


AristorLe inferred from his observations that all 
which now exists—the stars, the mountains, the trees, 
the animals—has developed into the present forms by 
a series of changes. This remarkable conception be- 
came material for the philosophers, but was never 
supported by observation; during the Middle Ages 
it was seldom defended or even mentioned. Up to 
1700 it was no more than a general theory of causa- 
tion—that is, the idea that all changes in the physical 
world are due to natural causes, not to miracles. 
By 1760 this theory had been applied particularly to 
plants and animals by several writers—notably by 
Buffon. In 1794 Erasmus Darwin speculated about de- 
velopment in these terms: ‘‘Would it be too bold to 
imagine that all warm-blooded animals have arisen 
from one living filament, which the great First Cause 
endued with animality?’’ The general theory of de- 
velopment was in the air, but it remained a vague 
philosophical conjecture. 

In 1809 (the very year of Charles Darwin’s birth) 
a brilliant Frenchman, Lamarck, published his Zoo- 
logical Philosophy, in which he described a theory of 
evolution that he had been brooding on for sixteen 
years. Here for the first time evolution was brought 
down from philosophy to be applied in a particular 
way to animals and plants. Lamarck was a thorough 
scholar and a hard worker, who was so well ac- 

267 


268 EVOLUTION FOR JOHN DOE 


quainted with the difficulty of classifying species 
that he felt there could be no hard-and-fast line be- 
tween them. It seemed to him that somehow the 
whole series of animals was like a continuous stream 
of forms that had developed from previous forms. 
His quick fancy framed a theory to account for such 
development—briefly this: 

Persistent use of any part draws the fluids of the 
body there, ‘‘and in proportion as the fluids are 
quickened in their movements, they alter the tissues 
in which they move’’; such changes in the body are 
inherited and tend to accumulate in_ successive 
generations. | 

This theory is based on ‘‘the effects of use and 
disuse’? and on the supposition that such effects 
(‘‘the acquired characters’’) can be inherited. It was 
a brilliant bit of imagining, put forth in a small book 
that could have been written in a few weeks, and it 
contains few efforts to supply facts in support of 
the reasoning. Lamarck belonged mentally to the 
eighteenth century, when it was thought that science 
could be spun out of an ingenious brain. In his early 
efforts at science his speculations about chemistry 
were ‘‘of a chimerical kind,’’ and he made ‘‘fruitless 
meteorological predictions.’’ In his latest efforts, 
when he reasoned about fossils, he poured out from 
his teeming brain the extravagant guess that all the 
rocks were made from the remains of animals. From 
youth to old age his mind was primarily fanciful. 

Yet he was much more than a wild fancier. His 
eyes were sharp and his intuition quick. However 
flimsy his reasoning might be, he had keen powers of 
perception. What he thought out he could express 
in a cogent and lively style. His book set the scien- 
tific world allagog. Its influence was strong for half a 
century—yes, for almost a century—captivating many 


LAMARCK 269 


trained minds. Its teaching could not be disproved 
by any facts that were then known to science, and it 
was so much in line with the natural suppositions 
about heredity that even Herbert Spencer espoused 
it and argued for it all during Darwin’s lifetime. In 
fact the teaching of Lamarck has not yet ceased its 
effect. 

The reason for this influence is not difficult to 
see. Lamarck had perceived a great fact that was 
hidden from all slow and conservative minds—to wit, 
that a species is not a fixed form of life, that there is 
no telling where one species ends and the next one 
begins. That is a great truth, and it is Lamarck’s 
glory that he saw it and put it vigorously before the 
world. What is more, no one could offer any sub- 
stitute to improve on Lamarck’s reasoning, His 
theory split the naturalists into three camps: those 
who followed him in believing that species changed 
by inheriting acquired characters; those who believed 
that species did not change by any process; those who 
thought that possibly species did change, but by some 
process that had not been discovered. If any intel- 
lectual man was imaginative and had no special 
knowledge of animals, he was likely to belong to the 
first Camp and be a Lamarckian; if a man was a hard- 
headed specialist familiar with facts, he was likely to 
belong to the second camp; if he was an exceptionally 
thoughtful naturalist, familiar witk the difficulties of 
classification, he would have leanings toward the 
third camp. The great majority of scientists be- 
longed to the second group—at least after 1840, when 
the spell of Lamarck had begun to wane. Two ex- 
amples will show this. Weismann says that when he 
was a young student in Germany during the late fif- 
ties it was bad form scientifically to take any stock 
in an evolution theory. When Huxley was a young 


270 EVOLUTION FOR JOHN DOE 


‘man and first met Darwin about 1850, he made the 
remark which he felt sure was the correct thing to 
say to a great scientist: ‘‘I believe that species are 
immutable.’? Thus Lamarckism was tried in the bal- 
ances for half a century and found wanting. 

Any sketch of the history of the Evolution 
Theory should at this point repeat in italics the prin- 
cipal feature of all discussions before 1859: No one 
disputed the possibility that acqured characters 
could be inherited. This was one phase of that ques- 
tion which has always been paramount and which ts 
not yet settled—‘What is variation???’ Lamarck 
assumed—all scientists assumed—that variation is 
the alteration produced in the body of an organism 
by use or disuse or by changed environment, and that 
such alteration is inherited. The eyes of all the dis- 
putants were turned to acquired characters. And to 
what else could they turn? There was nothing else 
in sight. 





CHAPTER XX 
DARWIN 


THE son of the Hrasmus Darwin mentioned in 
Chapter XIX settled in Shrewsbury, built up a large 
practice, and became well-to-do; but he inherited no 
acquired theory of evolution. He named his fourth 
child, born in 1809, Charles Robert, and hoped that 
the boy would continue the family tradition by enter- 
ing the medical profession. 

But Charles could not endure the horrors and the 
dullness of the Edinburgh school of medicine. So at 
the age of nineteen he was sent to Cambridge to be 
educated for the ministry. ‘‘I liked the thought of 
being a country clergyman,’’ he says in his autobiog- 
raphy, ‘‘and did not then doubt the strict and literal 
truth of every word in the Bible. Nor was this inten- 
tion ever formally given up, but died a natural death 
when, on leaving Cambridge, I joined the Beagle as a 
naturalist.’’ In the classics he had no interest, but in 
any sort of experimental science, or in the study of 
insects and birds and shells, in geometry, in Paley’s 
Natural Theology, he delighted. <A little episode of 
1831, just after his graduation from Cambridge, illus- 
trates Darwin’s way of regarding science. The Rev- 
erend Adam Sedgwick, an able professor of geology 
at Cambridge, visited the Darwin home on one of his 
expeditions for examining the ancient rocks. Young 
Darwin told him of a tropical shell that a laborer 
claimed he had found in a gravel-pit. Sedgwick 

271 


272 HVOLUTION FOR JOHN DOE 


thought that the shell had been brought there by some 
man, and added, ‘‘If it was really embedded there, it 
would be the greatest misfortune to geology, as it 
would overthrow all that we know about the deposits 
of the Midland Counties.’’ Darwin remarks, dis- 
ereetly and gently, that this attitude of mind pro- 
duced a strong impression on him. No wonder it did. 
For here was a man who valued a supposition more 
than a fact that would teach him the falsity of his 
supposition. Darwin’s mind always worked on the 
other tack and always prized any fact that would com- 
pel him to seek for new knowledge. 

Darwin at the age of twenty-two was an ardent 
sportsman and collector, affectionate, so tender- 
hearted that he would not take more than one egg 
from a nest or put a live worm on his hook, modest, 
reverent, clear-headed, and in rugged health. So 
good an observer was he and so enthusiastic that the 
professors of science took special notice of him and 
predicted a future for him. But his father could see 
no promise in the career of a son who seemed to care 
for nothing but shooting grouse and tramping thirty 
miles a day in the Welsh mountains. 

In 1831 a Cambridge professor recommended him 
for the position of naturalist on board the govern- 
ment ship Beagle, which was to take a trip around 
the world, making soundings for the admiralty 
charts. Darwin was glad of such a chance to follow 
his collecting mania, and for five years, without pay, 
performed his duties enthusiastically. Never was a 
country better served by any amateur scientist. 

A year after his return, in 1837, he settled him- 
self deliberately for an attack upon the great ques- 
tion, ‘‘How have animals become adapted to their 
ways of life?’’ We can not appreciate the ardor and 
severity of the twenty years of labor in seeking an 


DARWIN 273 


answer to the question unless we form some picture 
of his manner of life and work. He had inherited a 
considerable fortune and was free to live a life of 
ease, yet he chose a life of incessant toil. He con- 
ducted all manner of prolonged experiments with 
seeds and eggs and breeding of pigeons, observing 
the growth of plants, making minute measurements 
of bones and teeth, going carefully through great 
files of breeders’ journals and horticultural mag- 
azines, reading stacks of French and German scien- 
tific books, corresponding with all manner of men 
who might furnish him information, utilizing his 
daily walks for observation and experimenting—liv- 
ing every waking hour with the eager purpose of 
gathering more data. And all this unending labor 
was carried on against the greatest odds—for after 
1837 he never knew a day of the health that had been 
so bountiful in youth. His digestion had been im- 
paired by constant seasickness during his five years 
aboard ship; his nerves had been so much injured 
that even ordinary visiting was apt to excite illness; 
he was easily fatigued. Every morning he rose early 
and went to work, continuing at work as many hours 
as he dared; then he would rest as long as he was 
compelled to—never a minute longer. While he 
rested, he listened to reading. Every possible hour 
of labor was put in during every day of every year. 
All the skill of a tactful wife was exerted to keep his 
strength as great as loving care could make it. Until 
1842 he lived in the quietest London lodgings to be 
found, and after that he had a most secluded country 
home. No human life could have been more com- 
pletely devoted to one unremitting purpose. 

His practical and acute mind had never taken any 
stock in Lamarck’s easy-going answer to the riddle 
of evolution. He relates how one time when he was 


274. HVOLUTION FOR JOHN DOH 


only eighteen years old, as a young medical student 
in Edinburgh, he ‘‘listened with silent astonishment’? 
to an older student who ‘‘burst forth in high admira- 
tion of Lamarck and his views on evolution.’’ These 
views he thought were based on a very unsatisfactory 
kind of evidence. He thus describes his state of mind 
in 1837, when he began to ponder on his South Amer- 
ican observations of fossils and varying species: 


It was evident that such facts as these could only 
be explained on the supposition that species grad- 
ually become modified; and the subject haunted me. 
But it was equally evident that neither the action of 
the surrounding conditions nor the will* of the organ- 
isms could account for the innumerable cases in 
which organisms of every kind are beautifully 
adapted to their habits of life. I had always been 
much struck by such adaptations, and until these 
could be explained it seemed to me almost useless to 
endeavor to prove by indirect evidence that species 
have been modified. ... I worked on true Baconian 
principles, and without any theory collected facts on 
a wholesale scale, more especially with respect to do- 
mesticated productions. . . . I soon perceived that 
selection was the key-stone of man’s success in mak- 
ing useful races of animals and plants. But how se- 
lection could be applied to organisms living in a state 
of nature remained for some time a mystery to 
me... . Fifteen months after I had begun my sys- 
tematic enquiry I happened to read for amusement 
Malthus on Population, and being well prepared to 
appreciate the struggle for existence which every- 
where goes on from long-continued observation of the 
habits of animals and plants, it at once struck me that 
under these circumstances favorable variations 
would tend to be preserved, and unfavorable ones to 


*A reference to Lamarck’s ‘‘volition’’ or ‘‘appetence’? of animals 
—that is, the inward, unconscious impulse that he imagined directed 
animals in the line of their development. The idea is mot yet dead in 
the scientific world; see Chapter XXIV, Section IT. 





DARWIN 275 


be destroyed. The result of this would be the form- 
ation of new species. Here then I had at last got a 
theory by which to work; but I was so anxious to 
avoid prejudice that I determined not for some time 
to write even the briefest sketch of it. In June, 1842, 
I first allowed myself the satisfaction of writing a 
very brief abstract of my theory in pencil, in 35 
pages; and this was enlarged during the summer of 
1844 into one of 230 pages. 


Even in 1844 he had not fully decided that species 
develop by a change of previous species, for he said 
in a letter to Hooker: ‘‘At last gleams of light have 
come, and I am almost convinced (quite contrary to 
the opinion I started with) that species are not (it is 
like confessing a murder) immutable.’’ 

By 1856 the whole theory was clear in his mind, 
and he began to set it forth ‘‘on a scale three or four 
times as extensive as the Origin’’—which is itself 
six hundred and seventy pages long. Yet even this 
elaborate work, if he had carried it out as planned, 
would have been ‘‘only an abstract of the materials 
which I had collected.’’ He estimated that ‘‘my notes 
are so numerous during nineteen years’ collection 
that it would take me at least a year to go over and 
classify them.’’ 

In June, 1858, his work was interrupted by a most 
extraordinary letter. It came from a naturalist in the 
Hast Indies, asking Darwin to read an essay that was 
enclosed—an attempt to explain how species origi- 
nated. If evera letter was a thunderbolt, that one was. 
It was the most extraordinary coincidence in the an- 
nals of science, and all the events that led up to it 
multiplied the wonder of it. 

The naturalist who wrote it was Alfred Russel 
Wallace, an Englishman fourteen years younger than 
Darwin, whose life had been somewhat similar. At 


276 EVOLUTION FOR JOHN DOE 


the age of twenty-five he had gone on a collecting 
trip to the Amazon, and a few years later sailed for 
the Malay Archipelago, where he spent eight years. 
Like Darwin, he was struck by the bewildering array 
of new species, of confusing similarities, of difficul- 
ties of classification, of remarkable facts of distribu- 
tion, of the wonderful variety of adaptations for suc- 
ceeding in the tropical struggle for existence. Like 
Darwin, he had started abroad with the conviction 
that a species is an immutable form of life, but this 
belief waned as it encountered the horde of new facts. 
In 1855 he wrote an essay arguing that every species 
has been derived from a previous species: From 
that time his mind, like Darwin’s, was haunted by the 
question, “‘How could such changes come about?’’ 
One day early in 1858, while he was wrapped in blan- 
kets during a cold fit of a fever, he fell to ruminating 
on the same Malthus book that had started Darwin’s 
mind, and he began to consider the effects of the 
struggle for existence. ‘‘There flashed upon me,’?’ 
he says, ‘‘the idea of the survival of the fittest.’’ 
Thus Wallace in his blankets and Darwin in his ear- 
riage had seen the same revelation suddenly shine 
upon them as they stumbled over the same dark road 
of questioning. ‘‘If Wallace had had my sketch of 
1842,’’ wrote Darwin, ‘‘he could not have made a bet- 
ter short abstract. Even his terms now stand as 
heads of my chapters.”’ 

Here was a very delicate situation. Darwin’s pri- 
ority in reaching the theory was recorded in formal 
letters and was unquestionable, but he had not pub- 
lished any account of it. He argued that Wallace, if 
he had been in England, might very likely have pub- 
lished his essay, and so have appeared in the records 
of science as the first to formulate an evolution the- 
ory. This would have been the saddest kind of dis- 


DARWIN 277 


appointment to Darwin, a frustration of the ambition 
that is dearest to every scientist. But conscience told 
him that he must do for this young man what the 
young man might have done for himself if he had not 
put his fame in Darwin’s hands. Darwin resolved to 
have Wallace’s essay published, and to concede him 
the priority without explanation. ‘‘I felt angry at 
myself,’’ he confessed, ‘‘for not being able to repress 
a feeling of disappointment at what I thought was 
Wallace’s forestalling of my years of work.’’ 

This extravagant generosity (which would have 
been unfair to Darwin and a false honor for Wal- 
lace) was overruled by Lyell and Hooker, who acted 
as referees in the strange affair. They agreed to 
publish Wallace’s essay, for that was his due; but 
only on condition that some of Darwin’s sketch of 
1844 should be published with it, so that the two men 
should be linked in a joint report. They argued that 
they were deciding a question, not simply of the inter- 
est of one man or the other, but of the interest of 
science generally. 

This chivalrous handling of the delicate matter by 
Darwin and his friends is a charming episode in the 
history of science. Darwin and Wallace were firm 
friends for the rest of their lives, and Wallace be- 
came a useful and powerful champion of what he 
called ‘‘pure Darwinism.’’ He has had his full share 
of credit—perhaps more; for he never could have 
established the theory on any such firm foundation 
as Darwin was able to make for it. He had no such 
great quarry of facts from which to take building 
material, nor the power of mind to organize so wide- 
reaching an argument. His judgment was not of 
Darwin’s unerring quality, and hence he would not 
have been able to frame such a consistent whole out 
of the intricate and manifold data. At the Darwin 


278 EVOLUTION FOR JOHN DOE 


centenary in 1909 he thus described the relative 
credit that was due to himself and to Darwin: ‘‘My — 


share in the theory is to Darwin’s as two weeks is to 


twenty years.’? Such genial modesty has endeared ~ 


him to all the writers on evolution, so that they have 


been inclined to give him much more credit than he j 
ever claimed for himself. The progress of the theory | 


owes much to the knowledge and skill with which he 
argued for it. 

Darwin pushed forward his Origin as rapidly as 
possible and got the book through the press on No- 
vember 24, 1859. The first edition, one thousand, two 
hundred and fifty copies, was sold the first day. His 
diary records in December, ‘‘Multitude of letters.’’ 
To all his scientific friends he sent copies, and to 
other scholars whose opinions he valued. With these 
gifts he sent notes, the tenor of which is shown by the 
following sentences to Falconer: ‘‘Lord, how savage 
you will be if you read it, and how you will long to 
crucify me alive! I fear it will produce no other ef- 
fect on you; but if it should stagger you in ever so 
slight a degree, I am fully convinced that you will 
become, year after year, less fixed in your belief in 
the immutability of species.’’ 

How promptly and enthusiastically the best minds 
of the day felt the strength of the Origin has been in- 
dicated in Chapter XII. The fear and distrust of the 
new theory can be shown by quotations from two let- 
ters written shortly after its appearance. To John 
Lubbock, Darwin wrote: ‘‘There are so many 
weighty arguments against my notions that you will 


easily persuade yourself that I am wholly in er- . 


ror.... 1 dare say that when thunder and lightning 
were first proved to be due to secondary causes, some 
regretted to give up the idea that each flash was 
caused by the direct hand of God.’’ Lubbock did not 





DARWIN 279 


feel that such a reason was weighty and allied him- 
self with the Darwinians. But Sedgwick—the man 
who thought that the discovery of a fact might be a 
misfortune—wrote thus: ‘‘If I did not think you a 
good-tempered and truth-loving man, I should not 
tell you that I have read your book with more pain 
than pleasure. Parts of it I admired greatly; other 
parts I read with absolute sorrow, because I think 
them utterly false and grievously mischievous... . 
You write of ‘natural selection’ as if it were done con- 
sciously by the selecting agent.* ... . "Tis the crown 
and glory of organic science that it does, through 
final cause, link material and moral. You have ig- 
nored this link. . . . Passages in your book greatly 
shocked my moral taste. . . . I have written in a 
spirit of brotherly love, therefore forgive any sentence 
you happen to dislike; and believe me, spite of any dis- 
agreement in some points of the deepest moral inter- 
est, your true-hearted old friend.’’ 

Sedgwick’s fear was exactly what Darwin had 
prophesied when he spoke of thunder. To many de- 
vout minds of the eighteenth century Franklin’s ex- 
periments with electricity were morally disturbing, 
because Franklin seemed to deny that God directly 
ordained each clap of thunder. Scores of New Eng- 
land ministers felt that it was irreligious for science 
to investigate the instrument of God’s vengeance, 
just as scores had formerly felt that the law of grav- 
itation was opposed to religion. Hundreds of min- 
isters in the nineteenth century felt that it was irre- 
ligious to describe the adaptations of animals without 
reference to God’s direct ordaining of each one. Now, 
in the twentieth century, most ministers can see that 
the fallacy of these two fears is exactly alike. <As 


*From that day to this the same misunderstanding of Darwin’s 
metaphor has been frequent, 


280 EVOLUTION FOR JOHN DOE 


they look back on the periods of distrust, they see the 
pathos of it and wonder that teachers of religion 
should have been so blind. Yet we must sympathize 
with people who were afraid on moral grounds when 
such reasoning about gravitation and electricity and 
animals was new. 

Darwin’s feeling about this religious fear may be 
gathered from the following sentences of the descrip- 
tion which the vicar of Down, the Reverend J. Brodie 
Innes, gives of his thirty years of friendship with 
Darwin: ‘‘I had adopted the principle that the Book 
of Nature and Scripture came from the same Divine 
source, ran in paraHel lines, and when properly under- 
stood would never cross. Mr. Darwin’s views were 
very much to the same effect. The quaint conclusion 
of one of our conversations on religious subjects may 
be given; he said, ‘I do not attack Moses, and I think 
Moses can take care of himself.’ To the same effect 
he wrote more recently, ‘I can not remember that I 
ever published a word directly against religion or the 
clergy; but if you were to read a little pamphlet 
which I received a couple of days ago, you would ad- 
mit that I had some excuse for bitterness. The au- 
thor, a clergyman, sums up by saying that he has 
vainly searched the EKinglish language to find terms 
to express his contempt for me and all Darwinians.’ ”’ 

Some noted clergymen were friendly to Darwinism 
from the beginning, as shown by Charles Kingsley’s 
letter of 1859, quoted in Chapter XXV. But in the 
main the church was hostile for twenty years. Most 
thoughtful leaders of religious opinion must have 
ceased their attacks before 1900; for in 1894, at a 
small western college (then denominational), I was 
taught, both in the zoology class and from the pulpit, 
that evolution was not in conflict with religion, 


DARWIN 281 


It may be that personality has no place in science, 
but for my own part I find the individuality of Dar- 
win so interesting, and so unlike what might be 
guessed, that I shall venture to give some idea of it. 
In 1842 he took his family to a village twenty miles 
south of London, the hamlet of Down, which was ten 
miles from a railroad station and so secluded that he 
could be free from interruption by casual visitors. 
There he lived forty years, never missing a day of 
his beloved work unless his health failed. It is safe 
to say that during those years there was not in Eng- 
land any man whose home life was more beautiful, 
who was more genial and courteous, more honorable 
and affectionate in nature, or more devoted to the 
search for truth. 

The following quotations are taken from the 
sketch that his son wrote to preface a collection of 
his letters. 


He was delightfully tender to Polly, a rough, white 
fox-terrier, and never showed any impatience at the 
attentions she required, such as to be let in at the 
door or out at the verandah window. He was always 
rejoiced to get home after his holidays; he used 
greatly to enjoy the welcome he got from Polly, who 
would get wild with excitement, panting, squeaking, 
rushing around the room. He used to stoop down, 
pressing her face to his, and speaking to her with a 
peculiarly tender, caressing voice. 

I used to like to hear him admire the beauty of a 
flower; it was a kind of gratitude to the flower itself, 
and a personal love for its delicate form and color. I 
seem to remember him gently touching a flower he 
delighted in; it was the same simple admiration that 
a child might have. 

He once [when a boy] killed a hare sitting in the 
flower-garden at Shrewsbury by throwing a marble 
at it, and once, as a man, killed a cross-beak with a 


282 EVOLUTION FOR JOHN DOE 


stone. He was so unhappy at having uselessly killed 
the cross-beak that he did not mention it for years, 
and then explained that he should never have thrown 
at it if he had not felt sure that his old skill had gone 
from him. 

When he was excited with pleasant talk, his whole 
manner was wonderfully bright and animated, and 
his face shared to the full in the general animation. 
His laugh was a free and sounding peal, like that of a 
man who gives himself sympathetically to the person 
who has amused him... . To Huxley he once wrote, 
‘Hor your lectures I can give you a few amusing an- 
ecdotes and sentences if you want to make the audi- 
ence laugh.’’ 

I do not believe he ever spoke an angry word to 
any of his children in his life; but I am certain that it 
never entered our heads to disobey him. He kept up 
towards his children his delightful manner of express- 
ing his thanks; and I never wrote a letter, or read a 
page aloud to him, without receiving a few kind 
words of recognition. 

He drank very little wine. He had a horror of 
drinking, and constantly warned his boys that anyone 
might be led into drinking too much. 

It is impossible adequately to describe how de- 
lightful a relation his was to his family, whether as 
children or in their later life. It is a proof of the 
terms on which we were, and also of how much he was 
valued as a playfellow, that one of his sons when 
about four years old tried to bribe him with sixpence 
to come and play in working hours. We used to 
dread going in for sticking-plaster, because he dis- 
liked to see that we had cut ourselves, both for our 
sakes and on account of his acute sensitiveness to the 
sight of blood. He always made us feel that we were 
each of us creatures whose opinions and thoughts 
were valuable to him, so that whatever there was best 
in us came out in the sunshine of his presence. 

A few days after the death of his little daughter, 
Annie, he wrote: ‘‘We have lost the jov of the house- 
hold, and the solace of our old age. She must have 


DARWIN ( 283 


known how we loved her. Oh, that she could now 
know how deeply, how tenderly, we do still and shall 
ever love her dear, joyous face! Blessings on her.’’ 

When he gave his evidence before the Royal Com- 
mission on vivisection, he came out with his words 
about cruelty, ‘‘It deserves detestation and abhor- 
rence.’?’ When he felt strongly about any similar 
question, he could hardly trust himself to speak, as 
he then easily became angry, a thing which he dis- 
liked excessively. He was conscious that his anger 
had a tendency to multiply itself in the utterance, and 
for this reason dreaded having to scold a servant. 

The letters that he received gave him much pleas- 
ure, because he habitually formed so humble an es- 
timate of the value of all his works that he was gen- 
erally surprised at the interest which they excited. 
His happy choice of matter for talk seemed to flow 
out of his sympathetic nature, and humble, vivid in- 

terest in other people’s work. 
/ He undoubtedly had, to an unusual degree, the 
\ power of attaching his friends to him. 

His relationship to the village people was a pleas- 
ant one; he treated them, one and all, with courtesy, 
and took an interest in all relating to their welfare. 
Some time after he came to live at Down he helped to 
found a Friendly Club, and served as treasurer for 
thirty years. He took much trouble about the club, 
keeping its accounts with minute and scrupulous ex- 
actness. Every Whit-Monday the club used to march 
round with band and banner, and paraded on the 
lawn in front of the house.... Mr. Innes, the vicar 
of the church writes: ‘‘In all parish matters he was 
an active assistant; in matters connected with the 
schools, charities, and other business his liberal con- 
tribution was ever ready, and in the differences 
which at times occurred in the parish I was always 
sure of his support.’’ 7 

I must say something of his manner of working. 
He showed his love of saving the minutes in the dif- 
ference he felt between a quarter of an hour and ten 


284: EVOLUTION FOR JOHN DOE 


minutes’ work. ... I was often struck by his way of 
working up to the very limit of his strength, so that 
he suddenly stopped in dictating, with the words, ‘‘I 
believe I mustn’t do any more.’’... All these pro- 
cesses were performed with a kind of restrained 
eagerness. He always gave one the impression of 
working with pleasure, and not with any drag. 
have an image of him as he recorded the result of 
some experiment, looking eagerly at each root, and 
then writing with equal eagerness. ... I think he per- 
sonified each seed that he was counting as a small 
demon trying to elude him by getting into the wrong 
heap; and this gave to the work the excitement of a 
game. 

A few of his mental characteristics, bearing on his 
mode of working, occur to me. There was one qual- 
ity of mind which seemed to be of special and extreme 
advantage in leading him to make discoveries; it was 
the power of never letting exceptions pass unnoticed. 
It was just these things that he seized on to make a 
start from. . . . Another quality was his power of 
sticking to a subject. He often quoted the saying, 
‘“It’s dogged as does it,’’ and I think doggedness ex- 
presses his frame of mind almost better than perse- 
verance. Perseverance seems hardly to express his 
almost fierce desire to force the truth to reveal 
itself. ... He was willing to test what would seem to 
most people not at all worth testing. These rather 
wild trials he called ‘‘fool’s experiments,’’ and en- 
joyed extremely.... The love of experiment was very 
strong in him, and I can remember the way he would 
say, ‘‘I shan’t be easy till I have tried it,’’? as if an 
outside force were driving him. 

The tone of the Origin is charming, and almost 
pathetic; it is the tone of a man who, convinced of the 
truth of his own views, hardly expects to convince 
others; it is just the reverse of the style of a fanatic, 
who wants to force people to believe. The reader is 
never scorned for any amount of doubt which he may 
be imagined to feel, and his skepticism is treated with 
patient respect. A skeptical reader, or perhaps even 


DARWIN 285 


an unreasonable reader, seems to have been generally 
present to his thoughts. 

He speaks of all other authors as persons deserv- 
ing of respect. His respectful feeling was not only 
morally beautiful, but was of practical use in making 
him ready to consider the ideas and observations of 
all manner of people. In spite of having so strong a 
respectful feeling, he had the keenest of instincts as 
to whether a man was trustworthy or not. He 
seemed to form a very definite opinion as to the ac- 
curacy of the men whose books he read; and made 
use of this judgment in his choice of facts for use in 
argument or as illustrations. 

He had a keen feeling of the sense of honor that 
ought to reign among authors. He had a contempt 
for the love of honor and glory, and in his letters 
often blames himself for the pleasure he took in the 
success of his books, as though he were departing 
from his ideal—a love of truth and carelessness 
about fame. 


When Darwin died in the spring of 1882, a com- 
mittee of Parliament petitioned that he should be 
buried in Westminster Abbey, and the dean gladly 
assented. Among his pall bearers were Canon Far- 
rar, James Russell Lowell, the Duke of Argyll, and 
four of the scientists who had revered him, in the 
words of John Lubbock, ‘‘as their dear master,’? 


CHAPTER XXI1 
WEISMANN 


As we pass beyond Darwin’s period, it will be well 
to recall the seven evidences for evolution, in order 
to see how they fitted into the history of the develop- 
ment of the theory. Lamarck, in 1809, had to rely 
mainly on the evidence from classification and got 
hints from the evidence of structures. These could 
indicate to his lively mind that there had been evo- 
lution, but they could furnish no data as a proof. By 
the time Darwin settled himself to solve the problem 
there had been great advances in the knowledge of 
the fossil record and of the distribution of life in 
geological times and now. Darwin used these as a 
set of facts which challenged science to explain them, 
which admitted of no solution except evolution, but 
which did not furnish any key to the process of evy- 
olution. That key he found in artificial selection, 
and with it he opened the gates of the mystery. 

But the definite evidence that is in embryos was 
mostly hidden from him. He could divine its general 
nature, and he declared in 1860, ‘‘Embryology is, to 
me, by far the strongest single class of facts in favor 
of change of forms.’’ But further he could not see, 
for the realm of chromosomes was only beginning to 
be explored when he died. The knowledge of that 
field was the next great advance in the Evolution 
Theory. 

While young Darwin was going around the world 

286 


WEISMANN 287 


on the Beagle, August Weismann was born in Ger- 
many. He trained himself to be a physician, was 
made a professor of zoology, and devoted himself to 
studies with the microscope. So ardently did he use 
his eyes that they gave out, and for nearly ten years 
he was practically blind. But he did not allow the 
loss of sight to interfere with work. He had books 
read aloud to him; he pondered the problems of ev- 
olution, especially those raised by the Origin of Spe- 
cies; and he dictated essays on the central problem of 
them all—the nature of variation. One of the last 
labors of Darwin was to write a preface for the Eng- 
lish translation of these essays, which appeared the 
year he died. After this ten-year period Weismann’s 
eyesight was restored in large measure, and he con- 
tinued his researches into the nature of germ-cells. In 
1892 he completed a set of Essays on Heredity, which 
were influential in the laboratory study of evolution. 
Many Darwinians understood that this volume had 
‘‘upset’’ the Origin, and hence they were much per- 
turbed; many foes of Darwinism believed that it was 
now ‘‘overthrown’’ by the German professor of Frei- 
burg. What a commentary that statement is on the 
pugnacity of human nature! We seem always prone 
to assume that somebody is fighting—fighting on our 
side or fighting against us. The fact was that Darwin 
had kept track of the early work of the young German 
and had seen in him an ally. Nor had Weismann any 
idea of a conflict. He admired Darwin and paid 
homage to him as to one who had been a great ex- 
plorer of nature’s unknown territory and had accu- 
rately described the boundaries of one region. Weis- 
mann simply penetrated farther into certain aspects 
of it by the use of his lenses. Even if Darwin had tried 
to investigate with the microscope, his one life was not 
long enough to do more than his part of the task. 


288 EVOLUTION FOR JOHN DOH 


In 1902 Weismann published two volumes, The 
Evolution Theory, summarizing the lectures given 
during his forty years of investigation. In the pref- 
ace he explains his purpose: ‘‘In my introductory 
lecture in 1867 I championed the Theory of Descent, 
which was then the subject of lively controversy, but 
it was not till seven years later that I gave a short 
course with a view to aiding in the dissemination of 
Darwin’s views. Then very gradually my studies led 
me to add to the Darwinian edifice and to attempt a 
further elaboration of it. ... Not only are the vital 
units which we can perceive, such as individuals and 
cells, subject to selection, but those units that are too 
minute for our microscopes are subject to it like- 
wise. ... Many prejudiced utterances in regard to 
Natural Selection would never have been published 
if those responsible for them had had any idea of the 
inexhaustible wealth of phenomena which can only be 
interpreted in the light of this principle.’’ 

The truth was that Weismann had entirely corrob- 
orated Darwinism by his work in a new field and had 
given the quietus to Lamarckism. He proved—as 
Darwin never was able to prove—that acquired char- 
acters can not be inherited. He felt just as Darwin 
had felt about the effect of climate and food and ex- 
ercise, and he knew that Darwin had marshaled much 
evidence against their effects on heredity. What was 
most needed was some evidence about mutilations. 
So he proceeded to the very rational experiment of 
mutilating mice for a great many successive genera- 
tions; and showed that no amount of removing adult 
structures will remove anything from the heredity. 
He went very much farther. He showed that a series 
of generations is more than a chain of ancestry; it is 
a continuous stream of life that flows directly from 
germ to germ. To this current of heredity Weismann 
gave the name of ‘‘germ-plasm.’’ 


WEISMANN 289 


No one man, if he had had the use of the best eyes 
for fifty years, could have developed this theory by 
working alone. The germ-cells are so extremely 
small that the mechanism in them is at the limit of 
vision even with the aid of the best modern ultra- 
microscopes. Before a beginning could be made of 
the study of these cells a whole generation of ob- 
servers had to struggle for a knowledge of what cells 
are. Not till the Origin had been published was it 
generally known that a cell has to arise from a pre- 
vious cell, and not till 1873 was any picture drawn of 
the processes in the division of a germ-cell. In this 
long campaign for a knowledge of the cell young Weis- 
mann had been an eager volunteer, and during his ten 
years of blindness he followed its progress like a sol- 
dier in a hospital. When he was again able.to use 
his eyes, his interest was centered on the ‘‘carriers 
of heredity,’’ the stream of germ-cells. 

He did not make any notable contribution to what 
he called ‘‘the raw material of observation, which will 
never bring us any further on’’; he used his energies 
for seeing and interpreting the raw material that oth- 
ers had acquired by the minutest care in using the 
strongest eyes. He did not try to go beyond the in- 
ferences that must follow from what could actually be 
seen through his microscope. His reasonings were 
always lucid, with a canny appreciation of what facts 
must be; and they are often lighted up and humanized 
by touches of genial humor. The ‘‘germ-plasm the- 
ory’’ which resulted from twenty years of examining 
microscopical facts is briefly this: The material which 
determines every item of inheritance is not diffused 
through the whole germ-cell, but is contained in the 
nucleus of that cell. And even in the nucleus the real 
determining factors are limited to the chromosomes. 
Hach chromosome, or in some cases each section of 


290 EVOLUTION FOR JOHN DOE 


one chromosome, represents a complete individual. It 
can not be any vague aggregate of similar materials, 
which somehow develop into a complex organism; it 
must contain within itself as much organized complex- 
ity as the adult body, for it produces precisely, by 
fixed operations, all the minute details of the body. 
Such a chromosome individual he called an ‘‘id,’’ an 
abbreviation of zdtoplasm, an ‘‘identity mold.’’ Since 
an id determines every detail of the organism that is 
to develop from it, it must contain a preparation for, 
or a specification of, every detail—such, for example, 
as the color pigment of the eyes or the length of the 
finger-nails. Weismann had no hope that we could 
ever see these counterparts of structure, but he ar- 
cued that they must exist, for we can not conceive that 
the smallest of the inheritance items is caused by 
ehance. Hach of this infinite number of determining 
factors in an id he called a ‘‘determinant.’’ If (he 
says in effect) there are in every growing embryo a 
great number of cells developing into structural forms, 
there may well be among them a sort of competition 
for nourishment; some of them may, in the fluctua- 
tions of the supplies or in their changes of position, 
be more fortunate than others, and so develop some- 
what more vigorously than the specifications called 
for. In such a case there would be a variation in the 
animal that develops from that chromosome. This is 
no explanation of variation, and it is only a well-made 
guess; but it may be correct, and may carry us on one 
more step in our efforts to understand the ultimate 
nature of variation. 

The last refinement of the germ-plasm theory has 
not been confirmed. And indeed the mental picture 
of ids and determinants has been shown to be consid- 
erably unlike what modern research has discerned 
with better apparatus. But Weismann’s prime con- 


WEISMANN 291 


ception—of a stream of hereditary germ-cells that are 
kept isolated from body cells—has been helpful in a 
high degree, as the latest and greatest investigator* 
of cells testifies several times: ‘‘The first fruitful at- 
tempt . . . was made on purely theoretical grounds 
by Weismann in one of those brilliant essays on hered- 
ity which contributed in so important a way to the 
enlargement of our views concerning cytological re- 
search. . . . The fulfilment of Weismann’s predic- 
tion is one of the most interesting results of modern 
cytological research. . . . A vast and always grow- 
ing body of data supports the general conclusions 
drawn by Weismann thirty-five years ago.’’ H. H. 
Walter thus estimates what his work meant to science: 
“‘He led the biological children of Israel out through 
the wilderness upon a notable pilgrimage of. fruitful 
controversy.’’ 

The pilgrimage has been in that Chromosome Land 
that is described in Chapter VIII. The controversies 
are outlined in the three following chapters. 


*H. B. Wilson, The Cell, 1925, pages 500, 503, 576. 


CHAPTER XXII 
MENDELISM 


Waitt Darwin was preparing the Origin for the 
press, an Austrian monk, J. G. Mendel, was beginning 
a series of experiments on a phase of evolution with 
which Darwin had wrestled mightily—‘‘hybridizing,’’ 
the crossing of two varieties. Mendel had a mathe- 
matical mind and planned a statistical sort of experi- 
ment with bees and peas. The results of his work 
with peas have recently occupied a large part of the 
attention of many researchers in evolution. Though 
they were as simple and exact as A, B, C, they have 
been extended into a fearsome array of technicalities. 
The encyclopedias have long articles on Mendelism; 
books on genetics devote long chapters to the subject, 
illustrated with intricate designs to show the ‘‘heter- 
ozygous’’ possibilities; a whole field of advanced 
microscopy is based on Mendelism. Into such a whirl- 
pool of terminology no reader of this book would care 
to be plunged, but he may care to see what the heart 
of the matter is; and I will try to show that in the 
following paragraphs. 

Mendel worked for eight years with scientific zeal 
according to a perfectly simple plan, to secure a rec- 
ord of what happened when different kinds of peas 
were crossed. In order to make sure of clean-cut re- 
sults he decided to observe only the most obvious 
characters and those that were in contrasting pairs— 
for example, tall vines and short vines, wrinkled peas 

292 


MENDELISM 293 


and smooth peas, green peas and yellow peas, hard 
pods and soft pods. 

In the summer of 1857 he put the pollen of a tall 
plant on the pistils of some short plants and gathered 
the seed that resulted. Also he fertilized some tall 
plants with pollen from a short one. In each case 
there was a mixed inheritance, and of course the off- 
spring of next summer would naturally be mixed. It 
sounds simple—like the experiment of a bright boy. 
It will sound different if we consider that there was 
no man in the world wise enough to predict the result. 
The greatest botanists of that time could not have told 
what percentage of Mendel’s pea crop of 1858 was 
going to be short and what percentage tall. It is likely 
that every one of them—even including Darwin— 
would have guessed wrong. | 

Every plant was tall. At such a result Father 
Mendel must have been as pleased as he was aston- 
ished. Since the character of tallness appeared to 
dominate the character of shortness, he called it 
‘‘dominant’’; to the character that had receded out of 
sight he gave the name ‘‘recessive.’? He found that 
all the other pairs of characters behaved in the same 
way: smooth peas dominated the wrinkled kind; 
soft pod dominated the hard pod; yellow dominated 
green. 

If he had been attending only to the characters of 
tallness and shortness, he might have supposed that 
his experiment was at an end; but he was not deceived 
by the uniform outside appearances. He wondered if 
any hidden mixtures lay dormant in this crop of tall 
plants, and therefore kept their seeds to plant in 1859. 
Then a new marvel appeared: out of 1,064 plants there 
were 787 tall ones and 277 short ones; the characters 
were nearly in the ratio of three to one. And all the 
other pairs of characters showed the same result: the 


294 EVOLUTION FOR JOHN DOE 


ratio of smooth to wrinkled was about three to one, 
and the ratio of yellow to green about three to one. 

At this point, even if we confine ourselves to the 
one character of tallness, the complication begins. If 
the short vines of 1859 were fertilized from short 
vines, only short vines resulted in 1860; and the same 
was true for a third of the tall vines. But two-thirds 
of the tall vines yielded the same ratio as their parents 
-——thrée tall to one short. You can see how a math- 
ematician would revel in the fourth generation. His 
joy is cubed when he takes up the possibilities of cross- 
ing wrinkled peas with tall vines, and short vines with 
smooth peas, and short vines with hard pods—and 
all the rest of the possible combinations. 

But Mendel was not carried away by the pleasures 
of combining seven characters taken two at a time. He 
was bent on deciding one simple and highly important 
question: Are these characters inherited independ- 
ently of each other? His tabulations for the series of 
years proved that they were entirely independent—a 
tall vine might bear smooth peas, or vice versa; 
smooth peas might be in hard pods on tall vines, or 
smooth peas might be in soft pods on short vines. 

In 1865 Mendel printed his report in a local scien- 
tific journal and gave an ingenious explanation, which 
showed real insight, of the three-to-one ratio. But sci- 
entists paid no attention to him. Even if his report 
had been widely read, it might not have meant any- 
thing; for there was no knowledge in the world by 
which to interpret his statistics. In 1900, however, 
when his article was rescued from oblivion and com- 
mented on by great biologists everywhere, the ratios 
were seen to have a deep importance. They indicated 
the mode in which the determiners worked in the chro- 
mosomes of the germ-plasm. The explanation—uni- 
versally accepted now~~is that the dominant and re- 


MENDELISM 295 


cessive characters all depend on a mechanism that 
corresponds to Weismann’s determinants; that they 
are essentially independent unit builders; and that 
they may persist, strong and complete, in the germ- 
plasm, though they may not build any character in the 
body, but may remain dormant for generations. 
Weismann’s name for them is no longer used, because 
it represented an imaginary element of a chromosome; 
to-day the scholars say ‘‘factor’’ or ‘‘gene,’’ 

They picture the working of genes thus: When the 
blossom of a tall vine is fertilized from a tall vine, 
the resulting germ contains two genes whose work is 
to determine the height of the vine that sprouts from 
it; one comes from the father and the other from the 
mother; they are equivalent, and they produce a tall 
vine. Represent them by T T, The same condition 
holds in the ease of a germ that is descended from 
two short vines; represent the genes by t t. Now if 
the blossom of a tall vine is fertilized by the pollen 
from a short vine, there is a pair of unlike genes, T t. 
One takes precedence; the T gene produces a tall 
vine. But the t gene is not destroyed; it is latent in 
the germ, recessive, 

Suppose that next spring one of these T t flowers 
is fertilized from another T t flower. It appears that 
there is as much chance of distributing the genes one 
way as another. The result would be, if the law of 
chances held strictly, that in every four flowers one 
would have T T genes, one would have t t genes, and 
two would have T t genes, The first would produce 
a tall vine of pure breed, for there is no recessive gene 
of shortness in it; and the second would be a pure 
short vine. If these were kept apart and fertilized by 
their own flowers, they would forever breed pure tall 
vines and pure short vines. But the third and fourth 
vines, which are tall because of the dominant T gene, 


296 EVOLUTION FOR JOHN DOE 


carry the latent gene for shortness and will, when 
self-fertilized, produce short vines in every case where © 


the T genes happen to be excluded. Three out of four, 
on the average, will have a T gene and will be tall; 
one of the four will have no T gene and will be short. 
The ratio of the tall and the short vines is three to 
one—the familiar three-to-one ratio in a generation 
of hybrid plants or animals. 

Readers who wish to follow out the subject further 
from this simple beginning may consult the sixteen- 
page summary in L. L. Woodruff’s Foundations of 
Biology, or may read the extended treatment in H. EH. 
Walter’s Genetics. These books are by no means im- 





possible reading for a layman, and have good dia- — 


grams to illustrate many sorts of crossings. 

During the last twenty years the laboratories have 
teemed with Mendelian experiments on many sorts of 
animals and plants, and all reports confirm the laws 
that were discovered in the peas of the garden of 
Mendel’s abbey. It appears that all inheritance is a 
matter of building a new individual by the assembling 
of independent ‘‘unit characters,’’ which are, in many 
cases, determined by the combination of two genes; if 
these are at odds with each other (called ‘‘allelo- 
morphs’’), one gene will dominate, and the individual 
will show that character in its body. But the reces- 
sive character has been perfectly preserved in the 
reproductive organs and may emerge in the next gen- 
eration if there is the right crossing. The proof comes 
out prettily with the color-patterns of poultry or 
canaries, and with the fur of rats or mice. It has even 
been possible to get some observations on cattle and 
horses. Some of the freaks of inheritance in man no 
longer appear peculiar to a Mendelian, because he can 
see the operation of recessive characters. Here are 
two examples. (1) If a dark-haired father and a light- 


MENDELISM 297 


haired mother have eight children all of whom are 
dark-haired, it is seen that the light hair is latent in 
the children and may reappear in the grandchildren, 
even if the children should all marry dark-haired per- 
sons. (2) Color-blindness can not be inherited direct- 
ly from a ecolor-blind father; all the children of a 
color-blind father and a normal mother will be normal; 
but half of the sons of the daughters will be color- 
blind. If a normal man marries a woman who carries 
the recessive genes of color-blindness, all the sons will 
be color-blind, and all the daughters, though normal 
themselves, will have color-blind sons. 

Experimenters are now so familiar with these la- 
tent characters and with the laws of their appearing 
and disappearing that they know how to handle mixed 
races, to replace the recessive genes by dominant 
genes, and so to produce pure races. They understand 
why some kinds of fowls can never be pure. They can 
give useful advice to breeders. Through their micro- 
scopes they have seen the linking of chromosomes, 
have charted some of the sections of chromosomes that 
produce certain characters, and have gone far toward 
a preliminary acquaintance with the infinitesimal 
processes of building the mosaic of a new animal in 
a germ-cell. Few kinds of investigation give so much 
promise of further revelations. 

To us who understand little of the details of Men- 
delism it might appear that all recent investigations 
have not resulted in any great advance toward new 
conceptions of evolution. For Mendelians tell us that 
‘“‘the essential thing’’ which they have demonstrated 
is that the determiners move along in the stream of 
heredity largely unmodified, that they may segregate 
themselves as independent units, and that they build 
an individual out of their separate unit characters; 
and Darwin declared more than half a century ago 


298 EVOLUTION FOR JOHN DOE 


that **An organism does not generate its kind as a 
whole, but each separate unit generates its kind.’’ To 
us laymen these two statements sound similar. But 
scholars familiar with present researches see a vast 
difference between Darwin’s vague prevision and Mor- 
gan’s actual knowledge of heredity mechanism. An 
indication of what Mendelism means to-day is given 
in these sentences from a summary by William Bate- 
son: ‘*The breeder now knows what he is about and 
is able to interpret countless phenomena previously 
meaningless. . . . Hnormous improvements can be 
made by applying accurate knowledge to the breeding 
of even such old-established crops as wheat, oats, to- 
bacco, ete, If this is true of the crops which have for 
ages been the object of unremitting care, it will be 
understood that the cultivated plants of tropical re- 
gions offer limitless possibilities. The breeding of 
coconut, rubber, jute, cacao and many more has 
scarcely begun. . . . Genetic science shows primar- 
ily what can be expected, providing the breeder with 
an aim, and also indicates how it may be attained. 

. We may confidently foresee that the applica- 
tion of scientific method will in the case of the 
breeder’s art effect a change in magnitude no less 
than that which has been witnessed in the other in- 
dustries.’’ 

Bateson published his statement in 1922. In the 
same year an American woman, Maud Slye, pub- 
lished an article that reveals much more impressively 
the possibilities of Mendelism, Biological Evidence for 
the Inheritability of Cancer m Man.* For fifteen 
years Miss Slye has bred mice in a laboratory of the 





*The Journal for Cancer Research, April, 1922. I do not know 
that this article is reliable; later investigators may show that Miss 
Slye’s observation was faulty. But her method of work, showing the 
reliance that all physiologists place in Mendelism, furnishes an excel- 
lent illustration of possibilities. 


MENDELISM 299 


University of Chicago, trying to determine the nature 
of the inheritance of the different kinds of cancer. 
Without a knowledge of Mendelism her work would 
have been impossible; with this knowledge she has 
been able to explain what no records of human ances- 
try could ever have revealed, I will give a brief 
summary of her findings after explaining the nature 
of cancer. 

Cancer appears to be an inability of cells to stop 
forming when they normally should, If, for example, 
a person breaks the skin on his lip, the cells at that 
place begin multiplying to replace the injured tissue; 
when their work is completed, they would normally 
stop growing; but if they lack the mechanism that 
controls growth, they will continue to multiply and 
will form abnormal tissue that ramifies through the 
flesh. This tissue is cancer. 

Miss Slye finds that the absence of a mechanism 
for growth-control is inherited as a recessive. One 
of her many experiments will illustrate what this 
means. She mated a female that had cancer of the 
breast and lungs to a male that was known to have 
no cancer in his ancestry. In the first generation 
there was no cancer, since all the offspring had the 
dominant gene of non-cancer. But the recessive gene 
of cancer was in their germ-plasm and appeared in 
their descendants exactly according to the Mendelian 
formula. There were three lines of descendants: 
mice that never developed any cancer through fifteen 
generations; mice that were all cancerous; mice of 
mixed inheritance—some cancerous and some not. 
Other breeding experiments show strikingly how the 
Mendelian laws explain what would otherwise be 
baffling mysteries in the inheritance of cancer. ‘‘By 
the continued selective breeding of a heterozygous 
individual with a non-cancerous mate all occurrence 


300 EVOLUTION FOR JOHN DOE 


of cancer was held off until the thirteenth generation.”’ 
‘(When a given type or location of cancer is bred in, 
it can be manipulated with absolute accuracy by the 
type of selective breeding used. It can be made to 
hold off for any number of generations desired or 
to appear in the next generation.’’ 

It is hard to refrain from exclaiming about the 
possibilities for human welfare that may be revealed 
in further researches by the aid of Mendelism. This 
knowledge of heredity may be opening the way to a 
control of the most dreaded of diseases. Its future 
benefits to the race are beyond guessing. 


ee . 


CHAPTER XXIII 
DE VRIES’S MUTATIONS 


In rHeE late eighties Professor de Vries, a Dutch- 
man at the University of Wirzburg, began an inten- 
sive study of the sports of an evening primrose. In 
the course of a few years he saw this well-spring of 
variation spout out a number of new species and an 
endless series of varieties and sub-varieties. ‘T'o the 
new species that thus appeared he gave the name 
‘‘mutations.’? Beginning in 1900, he published a 
series of essays on his observations, which he col- 
lected under the title Mutationstheorte. In 1904 he 
lectured on the subject in America and prepared a 
large volume to expound his views of evolution, 
Species and Varieties: Their Origin by Mutation. 
The gist of his theory is that the smaller variations 
occur within narrow limits, that they fluctuate back 
and forth without progressing and do not develop into 
pew species, but that species originate at a sudden 
bound as sports—as ‘‘mutations.’’ 

This view had a great vogue. Though it was based 
largely on the observations of the one plant, and 
though it contained nothing essentially novel, many 
experienced botanists subscribed to it and paid hom- 
age to it. It was commonly spoken of as a sweeping 
revision of the Evolution Theory. 

Shrewder minds seem never to have been much 
impressed by it. Bateson thought that de Vries’s spe- 
cies were only kaleidoscopic combinations of unit char- 

301 


302 EVOLUTION FOR JOHN DOE 


acters. Within a few years it had been severely 
criticized by experimenters whose results were pub- 
lished in the Carnegie evolution series. 8S. J. Holmes 
said: ‘‘De Vries’s mutationstheorie gained acceptance, 
especially in America, with a rapidity which was quite 
unjustified. It was regarded with extreme suspicion 
by most students of taxonomy and distribution.’’ 

The suspicion was based on these facts: (1) that de 
Vries had hunted high and low before he could find 
such a mutating plant; (2) that his primrose was a re- 
cent arrival from America (probably about 1875) and 
was therefore in an artificial ‘‘sporting’’ condition; 
(3) that it had been a eultivated plant in America; (4) 
that de Vries could not draw any line between lesser 
mutations and greater fluctuations; (5) that his prim- 
rose gave every sign of being a hybrid, which was re- 
vealing latent recessives; (6) that American cultiva- 
tors of the plant saw some of his so-called ‘‘new 
species’’ spring into existence, and that these muta- 
tions therefore seemed like mere ‘‘periodic’’ or ‘‘eyer- 
sporting’’ varieties—the very sort of variation against 
which de Vries had cautioned amateur observers. 

The most curious shortcoming of the mutation 
theory is that it differs from Darwin’s only in de- 
gree.* Darwin repeatedly says that sports occur in 
nature and are probably one source of evolution. In 
several passages de Vries credits Darwin with under- 
standing these two elements, and he does not set up 
a denial of the correctness of Darwin’s analysis, He 
puts the case clearly on page 573 of Species and Vari- 
eties: ‘‘There are two possibilities, and both have 
been propounded by Darwin. One is the accumulation 

*In his earlier essays de Vries apparently meant that his muta- 
tions would supplant Darwin’s variations; but in 1904 he declares dis- 
tinctly and repeatedly that small variations do accumulate in accord- 


anee with Darwin’s theory; and he says that Darwin did recognize the 
sudden ‘‘galtations’’ or mutations, 


DE VRIES’S MUTATIONS 303 


of the slight deviations of fluctuating variability; the 
other consists of successive sports or leaps taking 
place in the same direction.’’ He says that his muta- 
tions ‘‘comply with the demands made by Darwin as 
to the form of variability which is to be accepted as 
the cause of evolution.’’ De Vries’s modest proposal 
to change the emphasis of Darwinism is in striking 
contrast with the extravagant opinions of some of his 
disciples; and even that proposal seems to be evapor- 
ating under recent examination. 

Jt will be appropriate to close this account of mu- 
tations by quoting what de Vries says of Darwin: ‘‘In 
honor of him who with unsurpassed genius and by 
unlimited labor has made his law the basis of sateen 
thought.”’ 


CHAPTER XXIV. 
HOW EVOLUTION STANDS TO-DAY 


I, The Microscope vs. the Field 


TE men who study evolution to-day work in many 
divisions at highly specialized labors. They are di- 
vided into two principal groups: those who study cells 
in a laboratory, those who dig fossils and collect speci- 
mens in the field. From their earliest years of 
academic training till they are gray in the service they 
live opposite kinds of lives and see nature from oppo- 
site sides. Naturally, therefore, if we hear of their 
disputes, their views seem to us conflicting, and we 
wonder whether Darwinism is being torn to pieces in 
an arena. 

It is this situation that Bateson was describing 
when he made an address at Toronto in December, 
1921. He could not have chosen a more pertinent 
topic. He handled it wisely and with good effect for 
an audience that understood him, calling their atten- 
tion to the rift in their ranks, to the need of getting 
together and sympathizing with one another. In- 
strong terms he spoke of how, if the estrangement 
continued, the men in the field ‘‘will feel the ground 
fall from beneath their feet, while we who look up 
from our work-tables may find our eyes dazzled and 
blinded.’?’ The conclusion of his speech was this: 
*‘Let us, then, proclaim in precise and unmistakable 
language that our faith in evolution is unshaken. Our 

304 


HOW EVOLUTION STANDS TO-DAY — 308 


doubts are not as to the reality or truth of evolution, 
but as to the origin of species—a technical, almost a 
domestic, problem.’’ 

Bateson’s address was widely celebrated in the 
newspapers. Of course a mere report of what he said 
would not have been entertaining news; so the papers 
filled their space with what I can only term a ‘‘cele- 
bration’? of the address. Who wants to read the 
‘‘nrecise and unmistakable language’’ in which a con- 
vention of scientists asserts its faith in the reality of 
evolution? Newspapers know that their readers will 
be much better off if they are told that ‘‘the theory of 
Darwin still remains unproved.’’ That typical case 
of the misunderstanding of the differences of opinion 
among scientists is a fine illustration of how evolution 
stands to-day: it stands unshaken in scientific opinion, 
but it is all shot to pieces in the opinion of the news- 
papers. 

Every intelligent editor ought to resolve to keep 
his sporting reporters away from scientific gather- 
ings, so that the meetings shall not be described in 
terms of an athletic contest. He ought to feel that 
scientific faith is of more importance than the do- 
mestic problems of science. Because the press has 
so systematically misled the public in its descriptions 
of the differences between the Batesons and the great 
body of zoologists, the Council of the American Asso- 
ciation for the Advancement of Science adopted the 
following resolution a few months after the garbling 
of the Toronto address: ‘‘No scientific generalization 
is more strongly supported by thoroughly tested evi- 
dences than is that of organic evolution.’’ That is 
where evolution stands to-day. 

Only one further comment is needed on the dif- 
ferences between the men of the microscope and the 
men of the field. Researchers who specialize for years 


306 EVOLUTION FOR JOHN DOE 


on the eggs of grasshoppers or the Arctic ice-sheets 
lose all the perspective that we laymen have. All spe- 
cialists are concerned with differences in the phases 
of evolution; when they write their articles and 
speeches they must emphasize the special differences 
between the departments of knowledge. Hence to the 
outsider they seem to be calling each other ignorant 
and to be tearing evolution to pieces. This view of 
ours is quite unlike what is in the scientist’s mind. 
All that we know about evolution he takes for granted; 
it is to him like an A, B, C. He assumes that the 
record in the rocks is a truism. ‘‘The lines of argu- 
ment converging to support the theory,’’ says Bateson, 
‘‘are so forcible and so many that no alternative can 
be entertained. The geologic record is conclusive.’’ 
Even Jacques Loeb, a biologist who made ‘‘sardonic 
war on the Darwinists,’’ did so, we are told by an 
admirer, ‘‘not because he disbelieved evolution; on 
the contrary, he held it to be a self-evident fact.’’ As 
to the general truth of evolution, there are no differ- 
ences between the workers at the tables and the work- 
ers in the rocks. They may be sardonic about details 
of how variation operates. They are at one as to the 
unmistakable fact that it operates. They are in com- 
plete agreement with the statement that if evolution 
were given up they could see no opportunity to seek 
for further knowledge of nature. 


II, Orthogenesis and neo-Lamarckism 


The skeptics described in this section are at the 
opposite pole of mental operations—they are meta- 
physicians. Though their speculations are diminish- 
ing and growing very thin, their mode of thought is 
still an element in discussion of natural selection and 
must have a place in an account of how evolution 


HOW EVOLUTION STANDS TO-DAY = 307 


stands to-day. It is an alluring mode of thought. It 
takes us out of the confinement of fixed laws of nature 
and shows us a prettier region. It was irresistible 
to John Burroughs. It makes a strong appeal to all 
of us who feel the attractions of poetry and philos- 
ophy. 

The name for this pleasing conception of evolution 
is ‘‘orthogenesis.’’ The best way to understand it is 
to approach it by way of the mind of primitive man. 
He necessarily assumes that all the forces of nature 
are persons. He can not possibly do otherwise. Be- 
fore he dares to cut down a tree, he must make a 
prayer to the spirit of the tree; he makes excuses to 
the soul of the bear that he has killed; he tries to 
coax the personality of the rain or to appease the 
demon who makes a drought. This way of peopling 
every part of nature is inevitable, for the savage can 
not conceive why anything but personalities should 
bring him blessings or cause destruction of his hopes. 
The whole progress of civilization has been a very 
slow realizing, in one stage after another, that a stone 
falls because of natural law, and that no one has ever 
encountered the spirit of a tree. All advance of hu- 
man knowledge has been farther and farther into the 
region where impersonal laws work, and where no 
other cause of actions can be discovered by the senses. 

Hivery step in such advance has caused bewilder- 
ment and fear. To deny that there is a spirit in the 
corn is a sacrilege against a deep faith. It takes 
away the natural and understandable human explana- 
tion, and it substitutes an impersonal law that is 
opposed to all our mental workings. Yet the demon- 
strations have been made, one after another. Edu- 
cated people in 1750 could not accept a mere cause- 
and-effect explanation of a comet. ‘‘How,’’ they asked 
with indignation, ‘‘could the operation of mechanical 


308 EVOLUTION FOR JOHN DOE 


laws, acting by blind chance, bring such a portent at 
such a crisis in human affairs? No, there is some 
deeper and more spiritual power manifested in a 
comet.’’ That is the appeal to which our minds are 
always sensitive—the horror of ‘‘blind chance’’ and 
the insistence on ‘‘a deeper power.’’ Yet by 1850 most 
educated people had abandoned the petty idea of a 
special force in comets, and had accepted the prosaic 
explanation of a mass of matter impelled by fixed, 
invariable laws. 

Every proposal to remove the spirit from any part 
of nature has always seemed to most of the people of 
that time to be a proposal to remove all spiritual mat- 
ters from our thoughts. But the progress of science 
has never meant that. The advance of the realm of 
fixed laws has only meant the removal of the individ- 
ual, local, petty, supernatural forces. We can not to- 
day reach a primary cause of all natural laws except 
by supposing some mentality or spiritual force that 
ordained them. Science has kept discovering, one 
step after another, that the controlling spirit is far- 
ther from our direct senses than had been supposed; 
and it is still enlarging our conception of the great 
extent of natural law. Yet it never expects to prove 
that there is nothing but mechanism in the universe. 
Jt is always increasing our awe at what must lie be- 
yond science. 

All this is familiar enough and needs no explain- 
ing here. I simply wish to be sure that it is recalled 
to the reader’s mind before he goes on. 

Many scientists—perhaps most of the best ones— 
ponder upon the forces that are beyond our senses. 
Every thinking mind must always be wondering, 
‘What is it all about? How does it all come to pass?”’ 
As soon as scientists come to the limit of mere mate- 
rial investigation they, like the rest of us, are at lib- 
erty to speculate on the how. 


HOW EVOLUTION STANDS TO-DAY 309 


Now there is a point in the study of variation 
where the senses fail us. When the most rigorous and 
materialistic scientist has seen the regional bands of 
chromosomes, he can see no farther; no eye has be- 
held the beginning of variation. The student of fos- 
sils comes to a point at which he can learn nothing 
more of the origins of those different species that 
developed and flourished and died. What made them 
vary in such an orderly way? There they are, dis- 
played to our wonderment, in a series that progresses, 
as it were, in a straight line of development. How 
was the line determined? Surely, says reason, it 
could not have come by blind chance. May it not have 
been that in the make-up of each organism at any one 
period there was some sort of guiding impulse, some- 
thing innate that directed the species on this straight 
line? That is logical. To this kind of reasoning has 
been given a name which means in Greek ‘‘develop- 
ment in a straight line’’—orthogenesis. 

I will give below a series of numbered paragraphs 
that will show, nearly in chronological order, the dif- 
ferent forms which this logic of straight-line develop- 
ment has taken in the thought of leading minds during 
the last hundred and twenty years. 

1. Lamarck outlined his theory of evolution in 
four laws, the first of which says, ‘‘Life, by its proper 
forces, tends’’—etc. That means that life has within 
itself some sort of force which is—like free will, for 
example—independent of mechanistic regularity. The 
second of Lamarck’s laws states that ‘‘A new organ 
results from a new want continuing to make itself 
felt.’’? Lamarck did not mean that the conscious. de- 
sire of an animal originated variations, but that an 
entirely unconscious impulse, a ‘‘want’’ of some organ, 
caused it to ‘‘move’’ in such a way that vital ‘‘fluid’’ 
was brought to that part and caused it to develop. 


310 HVOLUTION FOR JOHN DOE 


2. This ‘‘want’’ of an organ had such resemblance 
to a striving or purpose or will that it was regularly 
interpreted by thoughtful English scientists as a sort 
of ‘‘volition’’ within the organs, and their interpre- 
tation was natural and proper a century ago. How 
could they, in those early days of science, accept a 
mechanistic explanation? Their philosophy was deep 
ingrained in the mind of Darwin, so that he had to 
encounter it early in his reasonings toward a theory. 
He says, ‘‘It became evident that neither the action 
of the surrounding conditions nor the will of the or- 
gamsms (especially in the case of plants) could ac- 
count for the innumerable cases of adaptation.”’ 

3. Lamarck’s fundamental notion was often ex- 
pressed (in an ancient phrase) as ‘‘an internal power’’ 
or ‘‘a principle of improvement,’’ and this form of 
it was held strongly by such superior minds as Lyell 
and Hooker. It was a chief cause of their reluctance 
to accept such 4 purely mechanical explanation as 
Darwin’s natural selection. In one of the earliest let- 
ters that Darwin wrote to Lyell about the Origin he 
shows that Lyell has raised the old Lamarckian objec- 
tion to ‘‘blind chance,’’ for he writes: ‘‘The improve- 
ment of our cattle, pigeons, etc., does not presuppose 
or require any aboriginal ‘power of adaptation’ or 
‘principle of improvement’; it requires only diver- 
sified variability.”? There was the issue, clearly 
raised, that vexed the scholarly world. All could see 
the. great weakness in Lamarckian ideas which Darwin 
saw—it does not apply to plants; and some could con- 
cede that it is not a necessity of reasoning; but many 
nevertheless felt that it was a true philosophy of the 
causes of evolution. 

4. An eminent, able and influential ‘Ayiericnne was 
Professor Hi. D. Cope, of the University of Pennsyl- 
vania, who could not reconcile himself to Darwin’s 


HOW EVOLUTION STANDS TO-DAY 311 


natural selection, because, as he wittily put it, ‘‘Sur- 
vival of the fittest does not explain arrival of the 
fittest.’’ In 1887 he made a strong attack upon nat- 
ural selection, arguing that there was a definite in- 
ternal force which directed the evolution of a species 
by causing modifications, and that those acquired 
modifications could be inherited. He had thus frankly 
returned to Lamarckism, because he could not accept 
an explanation that depended on fixed mechanical 
laws. 7 

5. Cope’s Lamarckism is the latest survival of 
note that I can learn of. Since his day the ‘‘principle 
of improvement’’ has shrunk and has grown so dif- 
ferent from Cope’s ancient vigor that it is almost 
ghost-like. It has become ‘‘neo-Lamarckism.’’ It 
merely argues that ‘‘perhaps’’ acquired characters, 
‘‘in some unknown way,’’ may be inherited. And 
even on this possibility it lays very little stress. Its 
nourishment is in the conviction that natural selection 
is not a sufficient explanation, that there must be 
some kind of unknown power which directs the lines 
of development. H. H. Newman says in his Readings 
wm Evolution that ‘‘paleontologists almost universally 
lay hold of both Lamarckian and orthogenesis ideas.’’ 
A good example of them is Professor H. F’. Osborn. 
He is a stalwart figure, a thorough scholar, who has 
gone almost as far as any modern in the mechanistic 
conception of how life developed from inorganic sub- 
stances. He admits that ‘‘the prevailing opinion 
among most modern experimental zoologists is against 
orthogenesis,’’? and he is the stoutest champion of 
Darwinian evolution. Yet even this man says emphat- 
ically: ‘‘The gradual evolution of adaptive form is 
directly contrary to Darwin’s theoretic principle of the 
selection of chance variations.’’ His word ‘‘adaptive’’ 
means, as he himself has explained, orthogenetic, 


312 EVOLUTION FOR JOHN DOE 


6. In Lull’s Organic Evodlution (1921) there is 
a chapter on orthogenesis which states the issue with 
such perfect fairness and acuteness that we can not 
tell surely which way the author’s sympathies lean. 
He says that orthogenesis (as distinguished from 
ortho-selection) is an unproved theory, but that it may 
be proper to believe in a force which ‘‘determines’’ the 
direction of the variations. 

To most biologists it would seem that the results 
of evolution must usually appear as ‘‘straight lines”’ 
of development. Surely the little ancestor of all the 
horses varied toward shorter legs and longer legs, to- 
ward bigger side-toes and smaller side-toes; but the 
shorter legs and bigger toes were unfavorable in the 
struggle for existence, and so perished, leaving no 
record of themselves. All the successive variations 
toward larger legs and smaller toes were useful, were 
reproduced, and so were recorded in the rocks. The 
resulting evolution was in these ‘‘straight lines,’’ to 
be sure; but the lines were merely the successful rem- 
nants of variations in many directions. Natural se- 
lection destroyed all other lines. There never was 
an inward tendency to one line, but only an outside 
force which extinguished every line except that one— 
and it is this which the paleontologist sees. The egg- 
layers of the crickets on Long Island (see page 136) 
have no ‘‘tendency’’ or ‘‘vital principle’’ that directs 
them to develop in a straight line toward more or 
toward less length; they vary both ways in any group 
of crickets. What happens is, broadly speaking, that 
the conditions of temperature and soil on Long Island 
kill every cricket in a given locality if its egg-layer 
is less than so many millimeters long. If a certain 
Kuropean nuthatch had a bill less than such a length 
in a certain locality, it starved; hence all the bills, 
as the species ranged northward, were developed in 


HOW EVOLUTION STANDS TO-DAY = 313 


a straight line of change. But no ‘‘principle of de- 
velopment’? need be conjured up to account for the 
change; the nature of the cones that contained the 
birds’ food determined the course of development. 
So always. 

Orthogenesis does not explain anything. It is 
merely the last slight remnant of the primitive desire 
to imagine an explanation that is not mechanical. 


III. The Nature of Variations 


Since 1900 there has been a great deal of skepti- 
cism about the nature of variations. The Mendelians 
have challenged every old, easy-going opinion and 
have asked, ‘‘What proof is there that any new char- 
acter ever appears? What proof is there that varia- 
tions can be accumulated as Darwin supposed?’’ I 
will summarize the three principal reasons for such 
doubting. 

1. The mere rearrangement of genes. If a pouter 
pigeon and va carrier are bred, the hybrid offspring 
are not simply a combination of pouter and carrier; 
and if the hybrids are mated, their offspring are still 
less like the thoroughbred grandparents. It is found 
that after a few generations of such mixed mating 
the form may ‘‘revert’’ to the ancient ancestral type 
of all the artificial breeds of pigeons, and this fact 
suggests that, in spite of ‘‘breeding true’’ for many 
generations, no new type has really been created, but 
that careful breeding has simply collected or sup- 
pressed certain factors—that is, the genes. 

A similar conclusion is reached in the case of any 
other domestic breed of plants or animals that is hy- 
bridized. There seems to be a possibility of explaining 
the variations as mere rearranging of the genes that 
were present in the parent stock, It is hard to get 


314 EVOLUTION FOR JOHN DOE 


evidence of any new character that originates as a 
new gene. To some observers no change seems fun- 
damental; every change, they think, could be explained 
as a mere rearrangement of elements that have always 
been present. All the propagation of new varieties of 
wheat may be explained as a mere reassortment of 
the same old genes. A field of wheat is a mixed pop- 
ulation of different strains; if a Patrick Shirreff 
walks through it and detects one stalk that looks pecu- 
liar, and if he selects it and breeds it, what proof has 
he that anything new has been created by chromo- 
somes? May not the new variety be merely a bringing 
to the surface, or a new assortment, of the same old 
ancestral units that have always been in wheat? 

2. Pure lines. One noted investigator, Johannsen, 
bred several generations of beans in such a way that 
he removed all traces of hybridizing and secured a 
‘‘oure line.’’ The beans propagated from this line 
for many generations remained true to form; no new 
character appeared; no old ones disappeared. There 
was no hereditary variation in the pure line. Other 
experimenters secured similar results. Pure lines of 
animaleules showed no variations through many gen- 
erations, but seemed to have a set of characters ‘‘as 
rigid as iron.’’ There were published reports to the 
same effect about potatoes and barley and hens and 
garlic. Bateson announced that ‘‘Supposed variation 
is commonly nothing but the recurrence of a recessive 
form; more often the direct product of a cross.”? 

3. Fluctuations. When any ‘‘mixed’’ population is 
investigated, doubts of variation arise. Statistics 
show that seventy-two-inch men have sons who aver- 
age much less than that height, and that sixty-six-inch 
men have sons who average much over that height. 
The human population fluctuates about a mean height 
of sixty-eight inches. A pailful of a certain kind of 


HOW EVOLUTION STANDS TO-DAY = 815 


scallops collected at random shows great variation in 
the number of ‘‘ribs’’ on their shells: a few have only 
fifteen ribs and a few have nineteen, but the majority 
have seventeen; the number of ribs fluctuates about 
seventeen as a mean. A pailful of potatoes from sev- 
eral hills shows great differences in size, but there is 
a mean; the small ones will produce some large off- 
spring, and the large ones will produce some small 
descendants. De Vries wrote long chapters to con- 
trast this sort of ‘‘fluctuating variability’? with in- 
heritable mutations. He showed that ‘‘long-continued 
selection of fluctuations has absolutely no appreciable 
effect, that centuries and perhaps geologic periods of 
continued effort in the same direction are not capable 
of adding anything to the initial effect.”? J. A. Thom- 
son said that ‘‘fluctuations are inadequate ever to 
make a single step along the great lines of evolution,’’ 
and numerous writers have echoed the idea. 

But numerous writers have also defined ‘‘fluctua- 
tion’’ in a quite different way, pointing out the simple 
underlying truth of all variability—to wit: So far as 
fluctuations are bodily, due to environment, they are 
not material for evolution; but so far as they are 
germinal (as some part of them may be) they are in- 
heritable and are material for evolution. 

The skepticism arising from these three sources 
has been fruitful, for it has challenged careless 
assumptions and has made all reasoners about evolu- 
tion take heed. It has also had an unfortunate effect, 
for it has made general readers suspect that there is 
no longer any such thing as the inheritable variations 
on which Darwin built a theory. The public heard 
that Professor Jennings had ‘‘overthrown Darwin’? 
by showing that in a pure line of animalcules there 
was no inheritable variation; but: the public did not 
learn about the rest of his work. He did not take it 


316 EVOLUTION FOR JOHN DOE 


for granted that he had disproved natural selection by 
one series of experiments. He tried again with a 
different species, and here he found that in pure lines 
there was variation which could be accumulated by 
selecting through many generations. Few students of 
heredity would now deny that there may be variations 
in pure lines and that these changes may be inherited. 
But these changes must be ‘‘mutations’’ and not 
modifications—terms defined in the next paragraph. 

The scholars of to-day seem fairly well agreed, 
after two decades of the most thorough searching of 
evidence, that there is now ‘‘a new content in the 
problem of selection’’. and that ‘‘the appreciation of 
its limitations has but accentuated its possibilities.’’* 
They have winnowed the classes of variation and dis- 
carded the chaff of non-essential external appear- 
ances; the resulting scheme is in three groups: 

1. Modifications—changes in the body, acquired | 
characters. 

2. Combinations—reassortment of genes, not orig: 
inating any characters, but giving new combinations 
of old ones. These may be inherited. 

3. Mutations—appearances of characters that 
have not existed in ancestors, characters that are due 
to actual fundamental changes in genes. 

(A fourth group should be added for scholarly 
completeness—the ‘‘fluctuations’’ described above. 
These may be either modifications or combinations.) 

No modification can be inherited, since it is not a 
change in the germ-cell. A combination or a mutation 
may be inherited, may be selected, and may be mate- 
rial for new adaptations. 

The simplicity of the scheme of variations may 


*L, L. Woodruff’s Foundations of Biology. Pages 299-306 give a 
concise account of the kinds of variation; this has clarified my mind 
and has been effective in college classes, 





HOW EVOLUTION STANDS TO-DAY 317 


look suspicious to any one who has wrestled with the 
many confusing terms that have been current in the 
literature of evolution, but it is a really valid scheme. 
It does not attempt to classify all the different kinds 
of variation by their outward appearance, for nothing 
about heredity can be known from the appearance. It 
takes account only of the fundamental distinctions. 
First it sets aside all body changes (modifications) 
as having no part in evolution; then it recognizes the 
two different kinds of inheritable changes. 

The terms ‘‘modification,’’ ‘‘variation,’’ ‘‘fluctuat- 
ing variation,’’ and ‘‘mutation’’ have been used with 
such different meanings that an unwary reader may 
suppose, in passing from book to book, that authors 
are at odds with one another when they are in agree- 
ment. I shall attempt a brief explanation of the chief 
meanings that have been common. 

‘*Modification’’ was used by Darwin and Wallace 
to mean any sort of change in offspring which could 
be transmitted to descendants; it was synonymous 
with inheritable variation. Now it is restricted to 
changes in the body that can not be inherited. 

‘‘Variation’’ is, as it always has been, the generic 
name for any sort of way in which offspring differ 
from parents without any regard to whether the dif- 
ference is in the body or in the germ-cell. It should be 
realized that Darwin could not make the modern sharp 
distinction between bodily and germ-cell variation; 
he could only speculate on the probability that some 
variations were not inherited. 

‘“‘Wluctuating variation’’ or ‘‘fluctuation’’ often 
means in recent books a change back and forth about 
a mean, a change that does not cumulate to form per- 
manent alterations; but it is also used to include small 
changes of both kinds—modifications and inheritable 
combinations, 


318 EVOLUTION FOR JOHN DOE 


‘¢Mutation’’ was invented by de Vries. Originally 
he used it to describe an extreme variation that can 
be inherited, a notable sport, so different from parents 
that it deserves the rank of a new species or distinct 
variety, like the ancon sheep. A common synonym 
at one period was ‘‘saltation’’—that is, a sudden leap 
to a new variety. When de Vries found that he could 
not distinguish the degrees of mutation, but that very 
slight variations might be as fixed and distinct as the 
largest sports, he altered the meaning to include any 
change of the germ-plasm that is regularly trans- 
mitted. This is now the accepted meaning, but the 
original one still lingers in some books. 


Further knowledge of variation seems most likely 
to come from such work with the microscope as that 
in which E. B. Wilson and T. H. Morgan are now the 
leaders. They are looking directly at chromosomes, 
are learning more about them every year, are teaching 
a host of experimenters how to observe them; and 
there is the citadel of the mystery of variation. 

In this paragraph I place three judgments on the 
nature of variation. P. C. Mitchell, 1900: ‘‘ Although 
knowledge of variation has become much wider and 
more definite, the estimate in which natural selection 
is held has changed very little since Darwin and Wal- 
lace first expounded their theories. The advance of 
knowledge has supplied no alternative to the Dar- 
Winian principles.’’ C. C, Nutting, in an address 
before the Genetics Branch of the American Associa- 
tion for the Advancement of Science, December, 1920: 
‘‘Tn conclusion it seems to me that we are justified in 
maintaining that Mendelism and the mutation theory 
have neither weakened nor supplanted the Dar- 
Winian conception of the origin of species by means 
of natural selection.’’ S. J. Holmes, who wrote 


HOW EVOLUTION STANDS TO-DAY 319 


for the University of California Chronicle of July, 
1921, an admirable summary of recent opinion, lucid 
and penetrating: ‘‘The status of natural selec- 
tion has become more firmly established than it 
was in the time of Darwin. The studies of Wel- 
don, de Cesnola, Bumpus, Davenport, Tower, and 
Morgan have shown the actual operation of selective 
elimination. . . . The reproach of Lord Salisbury 
that ‘No man has ever seen it at work’ has now been 
definitely shown to be without foundation. . . . The 
discoveries in the few years that have elapsed since 
the publication of Bateson’s address [of 1914] have 
afforded positive evidence of its unsoundness. The 
discovery of multiple allelomorphs has lent strong 
support to the view that Mendelian characters are due 
to factor transformations instead of merely. gains or 
losses. Recent work has added further and critically 
tested evidence of the origin de novo of dominant 
characteristics. It has shown that recessive genes 
occasionally mutate to form dominant factors... . 
The mutation theory has been brought more nearly in 
accord with the conception of the origin of species by 
the gradual method, as outlined by Darwin.”’ 

Kven more significant than such testimonies are 
the two following quotations from men who are more 
familiar with the detailed study that has led to skep- 
ticism about natural selection. L. L. Woodruff, who 
has minutely studied heredity in animalcules, sum- 
marized his opinion thus in 1923: ‘‘Selection is not 
shorn of its importance either practical or theoretical. 

. . Natural selection may afford an explanation of 
the adaptations of organisms to their environing con- 
ditions.’’ IH. B. Wilson, whose work on cells is the 
standard authority quoted in reference books, gave 
this judgment in 1914: ‘‘To such minds [he was in- 
cluding his own mind] it will seem that the principle 


320 EVOLUTION FOR JOHN DOB 


of natural selection, while it may not provide a mas- 
ter key to all the riddles of evolution, still looms up 
as one of the great contributions of modern science 
to our understanding of nature.’’ 


IV. The Faith in Natural Selection 
‘* All the world now travels along the course Darwin established.’? 
—John Burroughs. 

According to the newspapers Darwin is always 
being ‘‘overthrown.’’ Indeed he has been bowled 
over so many times that I have wondered who sets him 
up again. The latest overthrower, strangely enough, 
is John Burroughs, who says in an Atlantic article of 
August, 1920: ‘‘Darwin has been shorn of his Selec- 
tion doctrines as completely as Samson was shorn of 
his locks.’’ 

But who sheared him? Where is this Delilah con- 
cealed? I can find the Philistines who would like to 
bind Darwin, but nowhere can I come upon any trace 
of his shorn locks or of the clever scientist who cut 
them off. 

Burroughs does not tell who betrayed Darwin. He 
names Weismann in one place, and this rouses our 
suspicion; but Weismann was a most downright and 
outspoken champion of Natural Selection. Instead of 
overthrowing anything Darwinian he says, ‘‘My 
studies led me to add to the Darwinian edifice.’’ The 
two volumes of his latest and greatest work testify 
unqualifiedly that Darwinism ‘‘stands on a secure 
basis of fact.’? Especially does Weismann insist on 
the prime importance of Natural Selection and of ‘‘the 
wealth of phenomena that can only be interpreted in 
the light of this principle.’’ He rests his own method 
and the hope of fame on it: ‘‘This extension of the 
principle of Selection to all grades of vital units will 
endure even if everything else in the book should 
prove transient. . . . The slow and gradual effects 


HOW EVOLUTION STANDS TO-DAY 321 


of Natural Selection can not be explained, so far as 
we know, in any other way.’’ 

Burroughs hints that de Vries may have been the 
wily one who lulled Darwin to sleep, but de Vries is 
not guilty. He recorded his loyalty to Natural Selec- 
tion unmistakably in 1903: ‘‘My work claims to be 
in full accord with the principles laid down by Dar- 
win. . . . The great principle enunciated by Darwin 
reigns supreme. fit 

Burroughs quotes against Dye a man who is 
president of the eaeieen Museum and a noted Co- 
lumbia professor, H. F. Osborn. But there does not 
live any more staunch warrior against the Philistines 
than this same Osborn, who declares in his Origin and 
Evolution of Infe: ‘‘That Natural Selection is con- 
tinually operating at every stage of the transformation 
there can be no doubt.’’ He testifies that ‘‘pure Dar- 
winism has been refined and extended and powerfully 
advocated by Weismann and de Vries,’’ and he pays 
homage to ‘‘the master mind of Darwin.’’ 

It might seem possible that Professor T. H. Mor- 
gan, the greatest of the chromosome explorers, was 
the wielder of the shears; for Burroughs quotes his 
remark that ‘‘the spirit of Darwinism, not its for- 
mule, is our best heritage.’’ This is so brought into 
the article as to make it sound suspicious, as if it 
might mean, ‘‘Darwin didn’t know much, but he was 
a fine fellow.’? What Morgan really thinks about 
Darwin as a scientist he has expressed thus: ‘‘Dar- 
win’s theory of Natural Selection still holds first 
place to-day in every discussion of evolution. . . . 
I heartily agree with my fellow biologists in ascribing 
to Darwin the first place in biological philosophy. 

. Stated in these general terms [that is, as I have 
stated it in Chapter IX] there is nothing in the theory 
of Natural Selection to which any one is likely to take 
exception.”’ 


322 EVOLUTION FOR JOHN DOE 


Baffled and disappointed by every name that Bur- 
roughs mentions, we might next guess that Darwin 
had been delivered up to his enemies by some religious 
argument. But Burroughs emphatically states that 
he does not want religion in nature; he can not believe 
in a ‘‘creator who controls’’; he rejects the idea that 
“the stream of variation is guided by a higher 
power,’’ and he declares that ‘‘we see nothing like 
purpose or will in nature’s scheme of things.’’ He 
says that we ‘‘float in a boundless sea of energy; and 
that is all we know about it.’’ For my part, I had 
rather be tied up at the old dock of Natural Selection 
than adrift on such an ocean as that. 

Amadeus W. Grabau is certainly one of the fore- 
most of modern geologists, and he is not in any way 
radical or peculiar or given to over-statement. In his 
scholarly two-volume Textbook of Geology (1921) he 
has a chapter on fossils, an exposition of the common- 
place facts, which closes with a sentence that is clearly 
intended to state a commonplace and undisputed 
truth: ‘‘The principle of Natural Selection has come 
to be of fundamental significance in all biological 
studies, and its discovery and announcement mark the 
beginning of a new epoch in the intellectual develop- 
ment of the human race.’’ 

Hdwin 8. Goodrich, Linacre Professor at Oxford, 
says in his chapter on Natural Selection, 1924: ‘‘The 
Darwinian theory still stands unassailable as the one 
and only rational and scientific explanation of evolu- 
tion by natural forces.’’ 

I have searched high and low for the reputable 
scientist who has cut off Natural Selection, and I can 
not find him. Bateson, to be sure, has snipped at it, 
saying in one of his articles that ‘‘the modern geneti- 
cist assigns to Natural Selection a subordinate and 
inconsiderable role.’? But his opinion, when con- 


HOW EVOLUTION STANDS TO-DAY = 323 


trasted with all the representative quotations given in 
this chapter, is scarcely Samsonian. Perhaps the 
vigor and wit of Cope’s onslaught a generation ago 
seemed to Burroughs like a complete destruction; for 
Cope was only three years younger, was much ap- 
plauded by his generation, and doubtless had a strong 
influence upon the middle-aged Burroughs. 

Burroughs himself rejoices in the enduring vitality 
of Natural Selection. In this very article he formally 
confesses his faith and hymns his praise: ‘‘I believe 
in the accumulation of variations. . . . Species have 
come to be what they are through Natural Selection. 
» « ~ Adaptability comes through this fight for 
life. . ... Natural Selection gives speed, strength, 
keenness; it works upon these attributes and tends to 
perfect them.’? And he concludes with tributes like 
this: ‘‘Darwin is still the most impressive figure in 
modern biological science. . . . His candor and de- 
votion to truth are a precious heritage to all mankind. 
He taught us how to cross-question the very gods of 
life in their council-chambers. . . . All the world 
now travels along the course he established.”’ 


V. Darwin Did Not Rely on the Inheritance of 
Acquired Characters 


The subject of this section is, in one way; so tech- 
nical a question that any reader should skip to the 
next chapter if the title rouses no emotion in him. 

The seemingly petty matter has assumed a curious 
importance in popular arguments about evolution. 
Since it is frequently stated* that Darwin ‘‘appealed 

*For example, in Herbert’s First Principles of Evolution: ‘*Dar- 
win fully acknowledged the effects of the environmental factors, and 
relied upon them in many cases.’’ Herbert uses ‘‘effect of the environ- 


ment’’—as Darwin and Wallace did—to mean inheritance of acquired 
characters. 


324. EVOLUTION FOR JOHN DOE 


to’? the inheritance of acquired characters or ‘‘fully 


endorsed it’? or ‘‘emphasized it,’? and since such in- | 


heritance is now a discredited theory, many general 
readers have gathered a vague idea that Natural 
Selection was built on a foundation that crumbled. 
The idea might seem, at first sight, to be warranted 
by Weismann’s way of putting the case in Volume I 
of The Evolution Theory: ‘‘Darwin believed the 
Lamarckian factor to be indispensable... . It 
seemed to him to offer the only possible explanation 
of the disappearance of characters. . . . He even 
directed his own particular theory of heredity to the 
explanation of this. supposed form of heredity.’’ 
Those detached sentences may sound as if Darwin had 
‘‘relied on the Lamarckian factor.’’ But in fact they 
mean nothing of the sort. Weilsmann’s pages, when 
read entire, bring out a different topic—to wit: ‘‘La- 
marck never so much as put to himself the question 
whether acquired characters can be inherited; he 
assumed it as matter of course. But Darwin accepted 
it, hesitatingly and cautiously, because there was no 
other way of explaining the disappearance of organs 
which have degenerated.’? Weismann was cham- 
pioning Darwin’s skepticism and seeking for proof 
that acquired characters can not be inherited. 
Another accusation brought against Darwin’s 
theory is that he would have nothing to do with La- 
marckism when he wrote The Origin of Species, but 
that later in life he changed his views and accepted 
the inheritance of acquired characters. This idea is 
used by L. T. More in The Dogma of Evolution. He 
says: ‘‘It is well known that Darwin changed from 
his early and passionate advocacy of natural selection 
as the sole and sufficient cause of evolution to the 
milder view that it was an important factor. . . . 
Only after facts had multiplied, showing the inade- 


HOW EVOLUTION STANDS TO-DAY = 325 


quacy of natural selection, did biologists begin timidly 
to take Lamarck’s doctrine seriously. If one can read 
the signs aright, we may expect to have an increasing 
attempt to explain the cause of evolution by the in- 
heritance of acquired traits.’’? Professor More hopes 
for a revival of Lamarckism. The starting-point of 
his hope is that Darwin changed his mind after writ- 
ing the Origin. Of course Professor More’s idea and 
the idea that Darwin relied on Lamarckism are con- 
tradictory and ought to cancel each other; but, 
strangely enough, they combine to produce a suspi- 
cion that somehow or other Darwin put too much faith 
in Lamarckism at some time or other, and thus viti- 
ated his book. Hence it becomes necessary to explain 
that Darwin’s views of the effect of the environment 
were perfectly consistent throughout the last thirty 
years of his life. 

Darwin was always doubtful whether any changes 
produced by the environment could be inherited. He 
could not deny flatly such a possibility, because the 
evidence in favor of it was unanswerable. (For that 
matter, the very latest writers on heredity do not dare 
to deny flatly.) Every one of the men whose judgment 
he most respected believed in the inheritance of char- 
acters that were produced by the environment. To 
stand out against such pressure would have been fool- 
hardy. To deny the inheritance of acquired characters 
in 1859 would have been to defy the universal convic- 
tion of the learned world. No voice was raised against 
such a belief until 1875, and no voice of authority until 
1881. Darwin had to accept it, but he did so grudg- 
ingly. 

Such grudging acceptance is not ‘‘basing a theory 
upon.’’ Nor did Darwin ever vary from his original 
position, which he thus described in a letter to Wal- 
lace, written in 1857: ‘‘I suppose some very little 


326 EVOLUTION FOR JOHN DOE 


effect must be attributed to such influences [of en- 
vironment], but I fully believe that they are very 
slight.’’ 

The only reason I can discover for asserting that 
Darwin’s views altered after 1859 is a passage written 
thirty years ago by Professor H. F. Osborn in From 
the Greeks to Darwin, page 240. Osborn declared that 
there was ‘‘a slow change of mind towards the la- 
marckian factor’? and quoted as evidence six lines 
from a letter of 1862 and four lines from a letter of 
1876. The supposed evidence in the first letter is this 
statement: ‘‘My present work is leading me to be- 
lieve rather more in. the direct action of physical 
conditions.’’ But the whole emphasis of Darwin’s 
correspondence at this period is indicated by a phrase 
in the sentence that follows this one, in which he says 
that the matter is ‘‘so confoundedly doubtful.’’ Less 
than four months afterward he wrote to Lyell: ‘‘The 
more I work the more satisfied I become with varia- 
tion and natural selection.’’ The second letter from 
which Osborn quotes is one that thanks Moritz Wag- 
ner for a copy of his essays, in the course of which 
Darwin says, ‘‘The greatest error which I have com- 
mitted has been not allowing sufficient weight to the 
direct action of the environment. . . . Your case of 
Saturna is one of the most remarkable of which I 
have ever heard.’’ This was Darwin’s way of being 
extremely polite toward a German, who was bom- 
barding him with Lamarckian evidence, at a time when 
his views were ‘‘meeting a good deal of opposition in 
Germany’? and when the Germans were ‘‘very con- 
temptuous.’’ Darwin showed the same kind of gentle, 
and rather excessive, deference to Wiesner and Nen- 
mayr. There are two other letters in which he 
expressed the idea that he has perhaps not given suf- 
ficient weight to the action of the environment. But 


HOW EVOLUTION STANDS TO-DAY = 327 


I can not find in the Life and Letters any other refer- 
ence to a change of opinion after 1872, nor even an 
indication that he was any more worried than he had 
always been about the Lamarckian possibilities. 

Professor Osborn’s passage has been so remark- 
ably influential* that it deserves a thorough rebuttal, 
but I will merely give a sample of the proof that it is 
mistaken. The proof is not in detached fragments of 
letters, but in Darwin’s books of this period. In the 
revised edition of Animals and Plants Under Domes- 
tication (1875) there is an elaborate display of evi- 
dence on both sides of the question, ‘‘Can the environ- 
ment produce inheritable variations?’’ He has forty 
pages of evidence against the effect of environment, 
and concludes thus: ‘‘When we reflect on these facts, 
we become deeply impressed with the conviction that 
in such eases the nature of the variation depends but 
little on the conditions to which the plant has been 
exposed. . . . We are thus driven to conclude that 
in most cases the conditions of life play a subordinate 
part in causing any particular modification—like that 
which a spark plays when a mass of combustibles 
bursts into flame—the nature of the flame depending 
on the combustible matter, and not on the spark. Pro- 
fessor Weismann argues strongly in favor of this 
view.”’ 

Darwin had thus early beeome familiar with the 
work of the young foe of Lamarck and rejoiced in it, 
for it corroborated what Darwin always consistently 
believed: that Natural Selection was not based on the 
inheritance of acquired characters. 

Any one who cares to examine another book that 
he revised with great care in 1875 (Insectivorous 


*For example, Professor More quotes the identical sentences and 
uses the Osbern verdict to help him in building a philosophical argu- 
ment. 


328 HVOLUTION FOR JOHN DOK 


Plants), and the book that he published in 1877 
(Forms of Flowers), will find just the same attitude 
toward heredity. In these two books he is dealing 
with plants, which are more responsive than animals 
to environment. In the first one I find no concession 
to the influence of environment. In the second one 
there are seven references to the effect of environ- 
ment: three statements that fertility is affected, three 
concessions that variation may be induced (though he 
says that he has no evidence of this), and one state- 
ment that the first step in the developing of clis- 
togamy was probably due to altered conditions. In 
opposition to these slight admissions—which would 
be made by most modern geneticists also—there are 
seven denials of the influence of environment, and 
four passages in which he expatiates on the working 
of Natural Selection; one of these, seven pages long, 
is exactly in the vein of the Origin. I am sure any 
unprejudiced reader of the books made between 1868 
and 1877 will feel that Darwin’s views on the La- 
marckian factor had not altered in the slightest 
during the twenty years since the letter to Wallace. 

In 1878 he stated the same position unequivocally 
to Semper: ‘‘When I published the sixth edition of 
the Origin. . . I went as far as I could, perhaps too 
far, in agreement with Wagner; since that time I have 
seen no reason to change my mind.’’ 

There is no evidence that his mind changed during 
the remaining four years of his life, and there is one 
striking letter which shows how, only nine months 
before his death, he wondered whether he had not 
gvone too far in admitting the possibility of the La- 
marckian factor. On July 19, 1881, he wrote to 
Semper: ‘‘Hoffman even doubts whether plants vary 
more under cultivation than in their native home and 
under natural conditions. If so, the astonishing varia- 


HOW EVOLUTION STANDS TO-DAY 329 


tions of almost all cultivated plants must be due to 
selection and breeding from varying individuals. This 
idea crossed my mind many years ago, but I was 
afraid to publish it, as I thought that people would 
say, ‘How he does exaggerate the importance of 
selection.’ ”’ 

Darwin was always fearful of being too fond of 
Natural Selection. He always conceded that the opin- 
ion of the whole scientific world must be deferred to. 
He never altered this adjustment of the elements in 
his theory. He based his theory on those variations, 
springing from unknown causes, that appear in 
heredity. 

Even Darwin’s queer attempt to guess at the cause 
of variation (the theory of ‘‘Pangenesis,’’ 1868) is 
consistent with his lifelong conviction about the two 
elements in heredity: only two of the fifty pages dis- 
cuss the transmission of acquired characters. The 
whole burden of the essay is that, in the main, inheri- 
tance is a matter of germ-cells which are formed inde- 
pendently of the environment, but which might 
conceivably be altered by a persistent environment 
acting through several generations. ‘Though every- 
body believed in the influence of the environment upon 
heredity, no one had previously explained how this 
was possible. ‘‘On any ordinary view,’’ said Darwin, 
‘Sit is unintelligible how changed conditions can cause 
inherited modifications.’? Darwin was probably the 
only scientist of that time who clearly saw how incon- 
ceivable such an effect of conditions was. 

So he undertook in ‘‘Pangenesis’’ to imagine a 
mode of inheritance that could justify the universal 
belief in the inheritance of acquired characters. The 
gist of his speculation is this: ‘‘Perhaps each cell, 
or each differentiated part, of the body throws off 
minute ‘gemmules,’ which are like germs of ‘hat part; 


330 EVOLUTION FOR JOHN DOE 


perhaps these gemmules are collected from all parts 
of the body to constitute the sexual elements, and 
when they are thus combined in a fertilized cell each 
one reproduces its part of a body in the embryo, and 
thus a new animal is built up.’’ 

Of course the ‘‘gemmule’’ part of Darwin’s guess 
was all wrong; it is an absurdity to a modern student. 
But Darwin knew that this part was a guess, and did 
not base any conclusion upon it. It was the rest of 
‘‘Pangenesis’’ which hit the essential fact: that in the 
minute germ-cells there are exact representatives of 
every detail of adult structure. If any one knows how 
ignorant the world was about germ-cells in 1868, be- 
fore the fertilization of an ovum by a sperm had been 
seen, he will marvel at Darwin’s ingenuity. ‘‘Pan- 
genesis’? declared the same central truth which is 
paramount to-day—that all variation is a matter of 
germ-cells, and that unless external conditions pro- 
duce an alteration in germ-cells there is no effect on 
inheritance. Darwin felt sure that somehow, by some 
kind of process, ‘‘An organism does not generate 
its kind as a whole, but each separate unit generates its 
kind. . . . Reversion depends on the transmission of 
dormant gemmules. . . . An organic being is a mi- 
crocosm—a little universe, formed of a host of self- 
propagating organisms, inconceivably minute and 
numerous as the stars in heaven.”’ 

That description, which seemed a mysterious and 
incredible fancy to most of Darwin’s critics in the © 
past century, is essentially like the facts seen under 
the microscope to-day. His imagined ‘‘units’’ in the 
germ-cell are now known as ‘‘unit characters.’’ The 
very name of ‘‘genes’’ was extracted from ‘‘pan gene 
sis’’ as a verbal tribute to the man who foresaw them 
in imagination. The ‘‘dormant gemmules’’ of Darwin 
have been christened ‘‘recessive genes’’ in the twen- 


HOW EVOLUTION STANDS TO-DAY = 331 


tieth century. Darwin was remarkably modern in his 
conception of the problems of heredity; he never 
‘‘relied on’’ the inheritance of acquired characters; 
he never altered his views about the elements of 
heredity. 


CHAPTER XXV 
THE FOSDICK IDEA 


Tr 1s now an antiquated custom to quote some proof 
that the most devout minds may see in evolution a 
noble and helpful conception. But the activity of Mr. 
Bryan and the response to his efforts indicate that 
such a chapter as this one may still be advisable. 

The testimony that the Reverend Charles Kingsley 
gave a week before the Origin went on sale might 
serve to epitomize everything that need be said on 
such a subject, or that has yet been said. He wrote 
to Darwin from the rectory at Winchfield to acknowl- 
edge the receipt of an advance copy. He addresses 
Darwin as ‘‘the naturalist whom, of all naturalists 
living, I should most wish to know,’’ and says, ‘‘If 
you be right, must give up much that I have believed 
and written.’’ Then he formulates the way in which 
he thinks a divine should regard religion and science: 
‘‘T have gradually learnt to see that it is just as noble 
a conception of Deity to believe that He created primal 
forms capable of self-development into all forms 
needful as to believe that He required a fresh act of 
intervention to supply the lacunas which He Himself 
had made, I question whether the former be not the 
loftier thought.’’ 

What Protestant has not heard of Henry Drum- 
mond? His Natural Law in the Spiritual World has 
been an inspiration to hundreds of thousands of 
Christians, and he accompanied the evangelist, Moody, 

332 


THE FOSDICK IDEA 333 


in many of his revival services. ‘‘If God comes upon 
the scene at special crises,’? says Drummond, ‘‘He 
is absent from the scene in the intervals. Is all-God 
or occasional-God the nobler theory? The idea of an 
immanent God, which is the God of evolution, is in- 
finitely grander than the occasional wonder-worker 
who is the God of an old theology.”’ 

As for the Catholics, their church has never pro- 
nounced against evolution. Every priest has always 
been free to believe in Darwinism or not. To give a 
view of what Catholics have done with the freedom in 
recent years I quote a few excerpts from a letter to 
the New York Times, written by Doctor Bertram C. 
A. Windle, of St. Michael’s College, University of 
Toronto. ‘‘The Church is neither committed to the 
crude and unthinkable Miltonie idea of creation, nor 
to the rigid ‘special creation’ view of Linneus. This 
entails an idea of species which is increasingly diffi- 
eult to hold. The Church has never expressed 
any opinion as to the method of creation. . . . From 
the time of St. Augustine of Hippo in the fourth cen- 
tury there has been a constant stream of suggestion 
that at the creation many, almost certainly most, liv- 
ing things were created, as he puts it, ‘potentially,’ 
and so as not then to appear, but only as an unfolded 
product when the time for them had arrived. Not, 
be it noted, by what is called very foolishly an ‘inter- 
ference.’ The clockmaker does not ‘interfere’ to make 
the clock strike when we hear it chiming out midnight. 
He made it just so that it should strike at that time. 
St. Thomas Aquinas centuries ago, but also centuries 
after St. Augustine, mentions this thesis with ap- 
proval; and in the best writings of to-day what the 
last important writer, Professor de Dorlodot of Lou- 
vain University (a paleontologist) calls ‘the moderate 
view} is adopted—a view which is exactly that which 


304. EVOLUTION FOR JOHN DOE 


was defined by Darwin himself when he wrote of ‘life 
with its several powers having been originally 
breathed by the Creator into a few forms or one, and 
that from so simple a beginning endless forms most 
beautiful and most wonderful have been and are being 
evolved.’ . . . Father Wasmann, 8S. J., the eminent 
authority on ants, and indeed on biology generally, 
when expressing his concurrence with this view says: 
‘My own conviction is that God’s power and wisdom 
are shown forth much more clearly by bringing about 
these extremely various conditions through the nat- 
ural causes of a race evolution than they would be by 
a direct creation of the various species.’ ... My 
second quotation shall be from M. de Dorlodot, be- 
cause of the regency of his book and because it bears 
the imprimatur of the rector of his university: ‘It 
seems to me that the more science progresses, the more 
audible becomes the voice of nature proclaiming the 
glory of its Creator. And among the heralds whom 
nature has used to make her voice heard, even to the 
ends of the earth, I think it just to place in the first 
rank Charles Darwin.’ ’’ 

I have called this chapter the ‘‘ Fosdick Idea’’ be- 
eause the thought in it has been most forcefully 
presented by the Reverend Harry Emerson Fosdick, 
who is a Baptist, a professor in the Union Theological 
Seminary, one of the best-known preachers of the 
day and one of the most effective in reaching 
young people, and author of several such devotional 
books as The Meaning of Prayer. If he is wrong, 
heaven help the church. IJ quote from the answer which 
the New York Times asked him to make to a com- 
munication that it had printed from Mr. Bryan, en- 
titled ‘‘God and Evolution.’’ Doctor Fosdick’s article 
has been reprinted in several religious journals. 


THE FOSDICK IDEA 330 


A large number of Christian people are quite as 
shocked as any scientist could be at Mr. Bryan’s sin- 
cere but appalling obscurantism. 

When he says, ‘‘Neither Darwin nor his sup- 
porters have been able to find a fact in the universe 
to support their hypothesis,’’ it would be difficult to 
imagine a statement more obviously and demonstra- 
bly mistaken. The real situation is that every fact 
on which investigation has been able to lay its hand 
helps to confirm the hypothesis of evolution. There 
is no known fact which stands out against it. 

The Bible is for Mr. Bryan an authoritative text- 
book in biology—and if in biology, why not in astron- 
omy, chemistry, or any other science, art, or concern of 
man whatever? One who is acquainted with the his- 
tory of theological thought gasps as he reads this. 
One had supposed that the days when such wild 
anachronisms could pass muster were passed, but Mr. 
Bryan is regalvanizing into life that same outmoded 
idea that the Bible is ‘‘the source of all science and 
arts including law, medicine, philosophy and rheto- 
ric’? Martin Luther attacked Copernicus with the 
same appeal which Mr. Bryan uses. He appealed to 
the Bible. He said, ‘This fool wishes to reverse the 
entire science of astronomy, but sacred Scripture tells 
us that Joshua commanded the sun to stand still, and 
not the earth.’’ 

One who is a teacher and preacher of religion 
raises his protest against this use of the Bible because 
it does such gross injustice to the Bible. When one 
reads an article like Mr. Bryan’s, one feels, not that the 
Bible is being defended, but that it 1s being attacked. 

The fundamental interest which leads Mr. Bryan 
and others of his school to hate evolution is the fear 
that it will depreciate the dignity of man.* Just what 


*Any one who eares to read an authoritative argument about this 
fear will not do better than to consult Evolution and Christian Faith, 
by H. H. Lane (Princeton University Press, 1923). Professor Lane 
has taught biology in two Christian colleges, ‘has been for thirty years 
a devoted worker in a Protestant church, and wrote his book in answer 
to a petition from students who asked, ‘‘What effect has acceptance of 
the theory upon religion?’’ 


336 EVOLUTION FOR JOHN DOH 


‘do they mean? Even in the Book of Genesis God 
made man out of the dust of the earth. Surely that 
is low enough to start, and evolution starts no lower. 
So long as God is the creative power, what difference 
does it make whether out of the dust by sudden fiat 
or out of the dust by gradual process God brought 
man into being? 

If one could appeal directly to Mr. Bryan, he would 
wish to say: Let the scientists thrash out the prob- 
lems of man’s biological origin, but in the meantime 
do not teach men that if God did not make us by fiat, 
then we have nothing but a bestial heritage. That is a 
lie, which once believed, will have a terrific harvest. 

The real enemies of the Christian faith are not the 
evolutionary biologists, but folk like Mr. Bryan who 
insist on setting up artificial adhesions between Chris- 
tianity and outgrown scientific opinions. The pity is . 
that so many students will believe him and will give 
up Christianity in accordance with his insistence that 
they must. 

It was in the eighteenth century that God was 
thought of as the absentee landlord, who had built the 
house and left it. The nineteenth century’s most 
characteristic thought of God was in terms of imma- 
nence—God here in this world, the life of all that lives, 
the sustaining energy of all that exists, as our spirits 
are in our bodies, permeating, vitalizing, directing all. 

Mr. Bryan proposes that we shall run ourselves 
into his mold of medievalism. He proposes, too, that 
his special form of medievalism shall be made authori- 
tative by the State, promulgated as the only teaching 
allowed in the schools. Surely we can promise him a 
long, long road to travel before he plunges the educa- 
tional system of this country into such incredible 
folly; and if he does succeed in arousing a real battle 
over the issue, we can promise him also that just as 
earnestly as the scientists will fight against him in 
the name of scientific freedom of investigation, so will 
multitudes of Christians fight against him in the name 
of their religion and their God. 


Tor Enp © 


BIBLIOGRAPHY 





BIBLIOGRAPHY 


Books in the first group are those most important 
for the layman who wishes to do some further reading 
of brief epitomes of evolution; in the second group are 
some useful books of a more technical kind; in the 
third group are certain books or monographs which 
are referred to in the notes of Evolution for John Doe; 
the fourth group names some texts that will give a non- 
scientific reader the fundamental facts of the different 
branches of biology. 


I 


1. R.S. Luu, The Ways of Infe, 1925. This is the 
most recent summary, by the best-known paleontologist 
in America, who has been highly successful and popu- 
lar in his college lectures, and who has ‘‘curtailed the 
technical language of science as far as possible’’ in 
his book. 

2. H. H. Newman, Readings in Evolution (1921), 
523 pages, with some illustrations. Different phases 
of the subject are presented by selections from thirty 
of the best authorities; the editor’s comments are im- 
partial and sound. An admirable book for general 
reference. 

3. A. R. Wauuace, Natural Selection, a collection 
of nine essays from 1855 to 1870, with some later ad- 
ditions and notes; the seventh essay contains the 
‘‘chart’’ which has been the outline of most elemen- 
tary teaching of evolution. 

4, JT. H. Huxusey, Lay Sermons and Addresses. 
Two of the chapters are the ‘‘Review’’ (1860) and the 
309 


a 


340 BIBLIOGRAPHY 


‘‘Criticism’’ (1864) which Huxley wrote in the early 
days of the controversy over the Origin. 

5. W.B. Scorr, The Theory of Evolution (1921), 
183 small pages. Six lectures summarizing the history 
and evidences. 

6. T. H. Morcan, A Critique of the Theory of 
Evolution (1919), four lectures in 197 small pages. 

7. oJ. W. Jupp, The Coming of Evolution, 1912, 


II 


Darwin, C. R., Origin of Species, which is supple- 
mented by The Variations of Animals and Plants 
under Domestication. 

Darwin, F., The Life and Letters of Charles Dar- 
win. This is charming in style and contents, and gives 
much information about the growth of the Evolution 
Theory. 

Houmes, 8. J., Present Tendencies in Evolutionary 
Theory, an article in the Unversity of Califorma 
Chronicle for July, 1921. A valuable summary, out- 
spoken but judicious, clear and forceful. 

Luu, RB. 8., Organic Evolution, 1921. 

Luu, Barrett, SchucHERT, Wooprurr, AND Hunt- 
ineton, The Evolution of the Earth and Its Inhabi- 
tants, 1920, 

Morean, T. H., The Physical Basis of Heredity, 
1919, 

Ossorn, H. F., The Origin and Evolution of Lnfe, 
JO2A 

THomson, J. A., Heredity, revised edition of 1919; 
System of Inanimate Nature, 1915. 

Vatss, H. pr, Species and Varieties: Their Orig 
by Mutation, 1904. 

Watiace, A. R., Darwinism, an Exposition of the 
Theory of Natural Selection, 1889, revised in succes- 
sive editions till 1912. 


BIBLIOGRAPHY 341 


Water, H. E., Genetics, 1923 (explains Mendelism 
fully, with many diagrams). 

Weismann, A., The Evolution Theory, 1902, trans- 
lated by J. A. and M. R. Thomson, 1904. 


TTT 


Carnegie Institution Publications, Nos. 49, 95, 101, 
1327143, 237, 

Gacrr, C. S., Heredity and Evolution in Plants, 
1920. 

Hersert, 8., The First Principles of Evolution, 
1916. 

JORDAN AND Kewtoae, Kvolution and Animal Life, 
1907. 

Lucas, F. A., Animals of the Past, 1920.: A read- 
able handbook, issued by the American Museum of 
Natural History, illustrated. 

MatrHew anp Cuuss, The Evolution of the Horse, 
1921. 

Nutratu, G. H. F., Blood Immunity and Blood Re- 
lationship, 1904. 

Wooprurr, L. L., Chapter VI of The Development 
of the Sciences, 1923. 


LV 


General Biology: Foundations of Biology, L. lL. 
Woodruff, 2nd, ed., 1923. This is the clearest and 
most readable compendium that I have seen, and is 
authoritative. It contains a good summary of the na- 
ture of heredity. 

Cells: The Cell, Hi. B. Wilson, 3d, ed., 1925. The 
work from which many books of reference have taken 
their diagrams. 

Animals: Zoology, T. D. A. Cockerell, 1921. An 


342 BIBLIOGRAPHY 


excellent elementary text-book, written with spirit and 
well illustrated. 

Plants: A Textbook of Botany for Colleges, W. F. 
Ganong, 1920. A very helpful book; its scholarship is 
infused with a zest for teaching. 

Fossil Plants and Animals: A Textbook of Geol- 
ogy, A. W Grabau, 1920. A large and rather technical 
book in two volumes; copiously and beautifully illus- 
trated. 


INDEX 


Aya t 


<n 
NP Are 


hia 


a i iy vt 





INDEX 


Abies, 217 
Acquired characters, 323-331 
other references, 110, 116, 117, 
137, 268-271, 288, 311, 316, 
327, 329 
Adaptations, 51-76, 145-156, 274 
other references, 42, 89, 92, 140, 
151, 162, 199, 200, 207, 210, 
237, 248, 272, 310, 311, 323 
pictures, 68, 69, 87 
Adjustments, see Adaptations 
Agassiz, A., 170 
Agassiz, L., 27, 170 
Albinos, 104, 147 
Alcoholism, 116 
Alfred, 167 
Alger, 23, 47 
Allelomorphs, 296, 319 
Almonds, 47 
Alpaca, 233 
American Museum of Natural His- 
LOL, 029) ) 09, iLL 15) 41 94200, 
207, 208, 236 
Ammonites, 187, 258 
Ameba, 99 
Amphibians, 156, 240 
Anatifera, 37 
Anatomy, 24 
see also Structure 
Ancestors, 236, 251 
Ancon, 101 
Angel movie, 195 
Animaleules 
eyes of, 155 
floating, 144, 145 
multiplying, 84 
variation in, 314 
Animals, see Sheep, Beetles, etc. 
Antelope, picture, 40 
Anthonomus, 34 
Antlers, picture, 102 
text, 94 
Ants, 46, 49, 64, 83, 88, 152 
Apples, 103 
Apricots, 47 
Aquinas, 333 
Archropteryx, 161 


Argyll, 285 
Aristotle, 21, 33, 267 
Arm, see Limb 
Armadillo, 116 
Artificial selection, see Selection 
Asphalt pit, 202 
Astronomy, 167 
Atoms, 123 
Auchenia, 233 
Augustine, 333 
Australia, 214 

see also Marsupials 
Azores, 211 


Backbone, see Vertebrates 
Bacteria, 23, 31, 70, 116 
Barbule, 65 
Barnacles, 34, 37, 48, 68 
Barrell, 195 
Bates, 106 
Bateson, 298, 301, 304, 306, 314, 
319, 322 
Bats, 58, 246-248 
Beagle, 271, 272, 287 
Beans, 94, 106, 314 
Bears, 22, 25, 61 
Beavers, 67 
Beebe, 242 
Bees, 58, 63, 66-68, 88, 154 
Beetles, 21, 34, 39, 63, 81, 106, 
143, 200, 204, 223, 227, 228 
Bennettitales, 220 
Bermuda, 60, 209 
Bernhardi, 85 
Bernheimer, 178 
Bible, 179, 335 
see also Religion 
Bills, 145, 312 
Biology, 341 
Bird man, 54 


_ Birds 


development of, 201, 237, 241, 
260, 262 

extinct, 161, 192 

other references, 28, 33, 52, 61, 
80, 87, 126, 127, 141, 145, 156, 
162, 210, 211 


345 


546 


Blacksmith story, 77 
Blaisdell, 228 
Blending, 224 
see also Series continuous 
Blood, 99, 123, 260 
Blood tests, 260-263 
Body, changes in, 315 
see also Acquired 
Environment 
Body-cells, 115-117 
Bohemian twins, 93 
Boll weevil, 35, 82 
Bones, 116, 117, 131, 177, 239, 247 
Botany, 342 
Bow-legs, 110 
Brassica, 131 
Brea, 202 
Breeders, 107, 128, 231, 297, 298 
Brontosaurs, 140 
Brussels sprouts, 132 
Bryan, 332, 335 
Bubonie plague, 48 
Buckwheat, 133 
Buffon, 184, 267 
Bugs, 40 
Bull-dog type, 141, 232 
Burroughs, 127, 157, 158, 307, 320, 
323 
Butterflies, 61, 62, 120, 146, 155 


characters, 


Cabbages, 22, 132 
Cactus, 24 
Calves, 94 
Cambrian, 186, 195-197 
Camels, 42, 52, 202, 234 
Camouflage, 61, 148 

see also Mimicry 
Canaries, 134, 142, 296 
Cancer, 298-300 
Cape Verde Islands, 213 
Caribou, 102 
Carnegie Institute 

341 

Castle, 135 
Cataclysms, 184 
Catalogue of Kew, 33 
Caterpillars, 48, 64, 81, 148 
Cats, 94, 111, 113 
Cattle, 101, 141, 232, 233, 296 
Cauliflower, 132 
Cells, 95-101 

other references, 31, 72, 224, 341 

picture of, 22 

see also Guard, Germ, 

Colony 


publications, 


Body, 


INDEX he 


Cellulose, 74 
Ceratium, 145 
Cereals, 131 
see also Corn, Wheat 
Chamberlin, 190 
Chance, 31, 130, 156-159, 308-311 
Characteristics, 111 
Characters, 111 
see also Acquired, Unit 
Chart 
of classification, 225, 228 
of evolution, 236 
of species, 204 
see also Tree of Life 
Chemistry, 174, 260-262 
Cherries, 234 
Chestnut blight, 106 
Christianity, 336 
see also Religion 
Chromosomes 
described, 97-101 
map of, 118 
of sex, 117 
other references, 104, 106, 108, 
109,\ 118,117, 120, 0120 ead 
143, 163, 286, 289, 297, 318 
size of, 122, 124 
with two patterns, 116 
Chrysanthemums, 132 
Clams, 44, 60 
Class, 34, 225, 226 
Classification, 32-39, 216-230 
other references, 24-28, 40, 43, 
47, 54, 55, 107, 250, 260, 262 
Claws, 149 
Clover, 69, 104 
Coal, 200, 240 
Cob, 119 
Cockerell, 102, 341 
Cockleburs, 69 
Cockroaches, 200 
Cod, 141 
Colony of cells, 75, 156, 224, 237, 
256 
Color-blindness, 297 
Colors, 53, 61-63, 67, 102, 104, 110, 
135, 143, 146-148 
see also Mimicry 
Combinations of genes, 296, 314, 
316 
Comets, 307 
Comstock and Troland, 123 
Continuous, see Series 
Cope, 310, 323 
Copernicus, 19 


INDEX 


Coral, 84, 178, 198 
picture, 23 
Corn, 22, 94, 118-120, 131, 234 
Corpuscles, 31, 260 
see also Blood 
Cotton, 82 
Crabs, 34, 139 
Crampton, 206 
Crane, 65 
Crickets, 38, 63, 136-139, 312 
Crocodiles, 185, 201 
Criiger, 68 
Cuvier, 185 
Cycles of life, 48 
Cytology, 95 
see also Cells 


Dahlias, 132 
Darning-needles, 200 
Darwin, Charles, 271-285, 323-331 
other references, 37, 38, 41, 50, 
Ga oosn L0d, Os, Lie 116; 
127, 142, 152, 157, 163, 188, 
189, 213, 232, 234, 286, 287, 
297, 302, 310, 313, 319, 334, 
340 
personality of, 280-285 
Darwin, E., 267, 271 
Darwin, F., 281, 340 
Darwinism, 277, 287, 288, 303, 304, 
311, 315, 318, 320 
Deer, 44 
Degraded forms, 59 
see also Parasites 
Dendy, 225 
Descent of animals, 236 
Design, 53, 54, 56 
see also Law, Savage way of 
thinking 
Determinant, 290 
Determiner, 294 
Devonian, 199 
De Vries, see Vries 
Diagram, see Chart 
Diatoms, 23, 65 
Diatryma, 19% 
Digestion, 23 
Dikdik, 40, 44 
Dinosaurs, 117, 178, 201 
Diseases, 23, 48, 116, 172 
see also Cancer, etc. 
Distribution, 204-215, 223 
Ditmars, 201 
Dogs, 22, 1138, 132, 222 


347 


Dominant characters, 
297, 319 

see also Mendelism 
Dorlodot, 333 
Dormant, see Heveesiees Reversion 
Down, 281 
Draba, 26 
Driesch, 254 
Drummond, 332 
Duekbill, 41, 47, 241 


293, 295, 


Dwarf, 93 
Eagles, 88 
Earth 


movement of, 18 
origin of, 190-202 
structure of, 193 
Eels, 52, 60 
Egeg- layers, 137, 154 
Eggs, 92, 100, ‘119, 243, 255, 257 
Einstein, 174 
Blan vital, 312 
Electrons, 123 
Eleodes, 227 
Elephants, 79, 153, 185, 202, 203 
increase of, 78 
Elk, Irish, 66 
Embryos, 252-259 


other references, 57, 92, 113, 
115, 119, 150, 246, 262, 286, 
290 


Environment, 114, 116, 131, 185, 
270, 288, 323, 324, 326-329 
see also Acquired characters 
Eohippus, 244 
Ether, 174 
Evidences, nature of, 167, 229, 254 
Evidences of evolution, 178-263 
Evolution 
chart of, 236 
defined, 16 
general course of, 156 
history of the theory, 267-312 
limits of, 15-16, 160-162 
never backward, 146, 249 
radiation in, 249 
retrograde, see Degraded forms, 
Parasites 
see also Selection, 
Variation, ete. 
to simpler forms, 59 
vs. any theory of how, 304-305 
Extinct species, 187 


Heredity, 


348 


Extinct species, con’t. 

other references, 28, 66, 162, 

183, 214, 223, 238, "251, "312 

Eyes 

evolution of, 148 

not perfect, 67 

series of, 154 

types of, 249, 250 


Fabre, 53 
Factor, 295, 319 
see also Gene 
Faleoner, 278 
Family, 34, 42, 207, 227 
Farrar, 285 
Feathers, 55, 64 
development of, 242 
Feet 
Chinese, 114 
marsupial, 103 
of fly, 65 
see also Five-finger 
Ferns, 83 
Fertilization, 52, 68, 92, 119, 295 
Field Museum, 222 
Finches, 207 
Finger, see Five-finger 
Fireflies, 58 
Firs, 217 
Fishes, 28, 52, 58, 60, 83, 94, 141, 
156, 198, 243 
Fitted, see Adaptations 
Five-finger structure, 246, 254 
Flickers, 55 
Flies, 48, 53, 63, 65, 67, 84, 118, 
135, 142, 147 
Flight, see Feathers, Wings, Five- 
finger structure, Membranes 
Floating arms, 144 
Flowers, 53, 67-69, 106 
Fluctuations, 314-317 
other references, 114, 121, 301, 
303 
Fosdick, 332-336 
Fossils, 178-190 
other references, 43, 177, 200- 
203, 215, 243, 245, 254, 312 
Fowls, 50, 296, 297 
Franklin, 54, 279 
Frogs, 44, 45 
Fruit-flies, 118 
Fungi, 23, 47, 67, 88 


Gager, 41, 341 
Galapagos, 207, 213 


INDEX 


Ganong, 23, 30, 70, 342 
Gaps between groups, 229, 239, 
242, 252 
see also Series continuous 
Gemmules, 329 
Genes, 295-298 
other references, 117, 289, 313, 
316, 319, 330 
Genotype, 317 
Genus, 34, 38, 39, 41-43, 204, 206, 
218, 220, 221, 226-228 
chart ‘of, 228 
Geographical, see Distribution 
Geologie record, 178-203 
other references, 28, 43, 57, 66, 
67, 88, 156, 191-202, 210, 
240, 245, 258 
see also Fossils 
Geology, 342 
Germ-cells, 115-124 
other references, 94, 99, 100, 
137, 142, 287, 289-291, 295, 
297, 329, 330 
see also Chromosomes 
Germ-plasm stream, 96, 120, 121, 
130, 288, 289 
Giant, 93 
Gills, 257 
Gingko, 42 
Giraffes, 111, 141 
Gliding, see Membranes 
Gold-fish, 106 
Goodrich, 187 
Goose, 105 
Gophers, 22 
Grabau, 195, 322, 342 
Grain, 131 
see also Corn, Wheat 
Grapes, 103 
Grasses, 24 
Grasshoppers, 81 
Gray, 218 
Great Barrier Reef, 23, 84 
Guanaco, 233 
Guard-eells, 72 
Guesses, 168, 239 
see also Theory 
Guinea-pigs, 135 
Gulliver, 122 
Gulls, 126 


Hairs 
animal, 121, 247, 296 
plant, 71, 100 
Hamlet, 124 





INDEX 


Hand, see Five-finger 
Hawkweeds, 26 
Hemlock, 217 
Hens, 50, 111 
see also Fowl 
Herbert, 323, 341 
Heredity, 109-124 
Mendelian, 294 
other references, 49-50, 
128-130, 134, 1438, 237 
see also Germ-cells, Genes, La- 
marckism, Variations, En- 
vironment 
Hereford, 101 
Hero-shrew, 116 
Herring, 83 
Heterotype, 228 
Hippopotamus, 185 
Histology, 95 
History, see Alfred, Earth, Geol- 
ogic record, Evolution 
Holmes, O. W., 258 
Holmes, 8. J., 302, 318, 340 
Hooker, 189, 277, 310 
Horned toads, 46 
Horses, 44, 79, 133, 153, 202, 222, 
240, 244, 296, 312 
Horse-shoe crab, 262 
Howard, 28 
Huber, 49 
Humming-bird, 67 
Hunger, 126 
Huxley, 245 
other references, 23, 38, 84, 150, 
161, 189, 244, 253, 255, 269, 
282, 339 
Hyacinths, 26 
Hybrids, 50, 292, 296, 302, 313, 
314 
Hypocephalus, 223 
Hypothesis, 155 
see also Theory, Science 


103, 


Ice-ages, 193, 196, 201 

Ids, 289, 290 

Increase of animals, 78-85 

see also Struggle for existence 

Indexes to geology, 187 

Infantile paralysis, 23 

Infection, 172 

Inheritable, see Heredity, Varia- 
tion, Acquired characters 

Innes, 280, 283 

Insects, 34, 48, 61, 107, 151, 156, 
204, 210, 211 


349 


see also Beetles, etc. 
Irises, 26, 151 
Islands, 208-215 


Jelly-fish, 238 

Jennings, 315 
Johannsen, 314 

Johnson, 143 

Jordan and Kellogg, 341 
Judd, 340 


Kazanloff, 93 
Kellogg, 341 

Kew Gardens, 33 
Kingdom, 33 
Kingsley, 280, 332 
Kipling, 60 
Koala, 53 


Lady-beetles, 143 
Lamarck, 267-270 
other references, 
286, 309 
Lamarckism, 268, 288, 324, 326 
see also Neo-Lamarckism, Ortho- 
genesis, Acquired characters, 
Environment 
Lamb, 94 
Landsteiner, 261 
Lane, 335 
Lava, 178, 182, 196 
Laws, natural, 31, 102, 159, 307, 
308 
see also Chance, Nature, Science 
Leaf expedition, 69 
Leaf-hoppers, 40 
Leaves, 67 
Leg, see Limb, Five-finger 
Lemmon, 220 
Lichens, 47 
Life, nature of, 31 
see also Origin, Nature, Prog- 
ress, Parasites, Web, Tree, 
Classification, etc, 
Lilies, 24 
Limbs, 240, 247, 255, 312 
see also Five-finger 
Line, 314 
see also Pure 
Lingula, 120 
Links between groups, 239, 243 
see also Gaps 
Linneus, 27, 28, 35, 36 
Lizards, 58, 61, 66, 210, 222 
Llama, 233 
Lobsters, 34, 149-150, 156, 254 


36, 37, 273, 


390 


Loeb, 306 
Logie, 154, 175 
see also Thinking 
Long, 85 
Long Island, 209 
Lost World, 179 
Lowell, 285 
Lubbock, 278, 285 
Lueas, 117, 236, 341 
Luck, 157 
see also Chance 
Lull, 131, 254, 312, 339, 340 
Lumpers, 11, 15, 38, 39 
Luther, 335 
Lutz, 38, 134, 136, 142 
Lyell, 188-190, 277 310, 326 


Madagascar, 214 
Maeterlinck, 58 
Magro, 93 
Malaria, 48 
Malthus, 274, 276 
Mammals, 28, 46, 156, 241, 244, 
247, 248, 257 
see also Whales, Squirrels, ete. 
Mammoth, 223 
Man, 201, 237, 257, 262, 335 
Mantis, 64 
Marquis wheat, 102 
Marsh, 244 
Marsupials, 41, 47, 52, 53, 214 
picture of feet, 103 
Mastodons, 203 
Materialism, see Mechanism, 
Chance, Religion, Laws natural 
Matthew and Chubb, 341 
Mechanism, 124, 308-311 
Membranes for gliding, 58, 242, 
248 
Mendelism, 292-300 
other references, 313, 318 
picture of, 237 
Mesozoic, 187 
Mice, 288 
other references, 112, 133, 296, 
299 
Michelson, 174 
Migration, 60, 154, 205 
Milkweed, 69 
Miller, 261 
Mimicry, 61, 68, 147 
Mitchell, 318 
Modification, 316, 317 
Darwin’s use of, 329 


INDEX 


Modification, con’t. 
other references, 93, 163, 274, 
327 
Molecules, 70, 71, 123 
Mollusks, 28, 156 
see also Snails, ete. 
Monkey doctrine, 15 
Monstrosities, 93, 94 
Mood, 103 
Moorea, 206 
More, 324, 327 
Morgan, 117, 142, 298, 318, 321, 
340 
Mosquito, model of, 69 
Mosquitos, 89 
Mosses, 28, 24 
Moths, 48, 61, 67 
Motion picture of geology, 195 
Mountains, 194 
Mud-puppy, 252 
Murchison, 186 
Museums, see American, ete. 
Mustard, 132 
Mutant, 105 
Mutation, 301-303, 317 
other references, 105, 315, 316 
Mutilations, 112, 114, 288 


Nahant, 68 
Nail story, 77 
Natural selection, see Selection 
Nature, 86, 113, 124, 129 

see also Laws natural 
Nautilus, 198, 258 
Navel orange, 102 
Nectarines, 47 
Neo-Lamarckism, 306-313 
Neumayr, 326 
Newman, 311, 339 
Newspapers, 305 
New Zealand, 214 
Niata, 232 
Noah’s flood, 179, 181 
Nucleus, 96-98, 110, 117, 260, 289 
Nuthatch, 145, 312 
Nutmeg, 140 
Nuttall, 261, 341 
Nutting, 318 


Oceans, 194 

Odors, 53, 67, 146 
Oranges, 94, 101, 106 
Orchids, 24, 68, 151 
Order, 34, 225, 226 
Ordovician, 197 


INDEX 


Origin of life, 15, 156, 160, 237 
Origin of Species, 324-328 
other references, 20, 50, 188, 
190, 232, 275, 278, 284, 287, 
332 
Ornithorhynchus, 241 
Orthogenesis, 306-313 
Ortho-selection, 312 
Osborn, 150, °208, 311, 321, 326, 
340 
Otter-hound, 132 
Ovipositor, 136 
see also Egg-layer 
Owls, 114 


Paleontology, 121, 177, 245, 311, 
340 


see also Fossils, Geologie record 
Paleozoic, 201 
Paley, 271 
Palms, 24 
Pangenesis, 329 
Paramecium, 84 
Parasites, 48, 59, 133, 161 
Partula, 206 
Peabody, see Yale 
Peaches, 47, 94, 103 
Peacocks, 62, 104 
Peas, 292-296 
Perfection, 162 
see also Adaptations 
Perfume, 67 
see also Odors 
Permian, 200 
Pests, 89 
Petals, 129 
Phalanger, 41, 47 
Phenotype, 317 
Phosphorescence, 84 
Photosynthesis, 71, 72 
Phylum, 34, 225-227, 250 
Picea, 217 
Pigeons, 80, 108, 120, 133, 273, 313 
Pigs, 104, 133, 134, 141, 222, 232 
Pinacate, 52 
Pines, 25, 43, 114 
Pistils, 67, 119 
Pitcher-plants, 45 
Planetesimal hypothesis, 192 
Plant-lice, 46, 48 
Plants, 24-25, 33, 47, 59, 192, 229, 
342 
flesh-eating, 45 
monstrosities in, 94 


301 


Plants, con’t. 
see also Peas, Pores, ete. 
Plums, 102 
Pointers, 111 
Poisons, 154 
Pollen, 61, 67, 68, 100, 119 
see also Flowers, Bees, Fertiliza- 
tion 
Pores, 67, 70, 71 
Porpoises, 46 
Potato-beetles, 81, 107 
Potatoes, 66, 104, 315 
Pratt, 27,28, 30 
Primates, 237 
Primroses, 105, 301 
Progress, 15, 161 
Proportions in evolution, 150 
Protophyta, 31 
Protoplasm, 73 
other references, 71, 95, 96 
Protozoa, 22, 31, 237 
Pterodactyls, 160, 247 
Pure lines, 314, 315 


Rabbits, 42, 61, 79, 88, 135, 222 
Race, 133, 231, 233 
Ram, 101 
Rana, 44 
Rancho la Brea, 202 
Rape, 132 
Rats, 44, 79, 142, 237, 296 
Rattle, 155 
Reason, see Logic, Thinking, Sav- 
age thinking, Laws natural, 
Religion, Mechanism, Chance, 
etc. 
Recapitulation theory, 
256, 259 
Recessive, characters, 293 
other references, 295-297, 314, 
319, 330 
Recombinations, 103 
see also Combinations 
Religion, 16, 19, 32, 161, 179, 278, 
279, 307, 322, 332-336 
see also Lane 
Remnants, 247 
see, also Vestigial 
Reptiles, 28, 156, 162, 200, 201, 
241, 243 
extinct, 130, 131, 140, 141 
flying, 160, 241, 247 
Reversion, 50, 116, 120, 313 
Rhinoceroses, 48, 52, 185, 193 
Rivalry of scientists, 169, 263 


150, 254, 


O02 


Robins, 87 
Rockhill, 103 
Rocks, 178-203 
age of, 182 
formation of, 193-194 
see also Geologic record, Fossils 
Romanes, 142 
Roosevelt, 62 
Roots, 69 
Roses, 26, 49, 128 
Rudimentary structures, 247 
see also Series continuous 


Saber-tooth tiger, 66, 87, 203 
Salmon, 59, 125 
Saltation, 302, 318 
Sap, 69, 72, 73 
Sargasso Sea, 242 
Saturnia, 326 
Savage way of thinking, 56, 76, 
104, 186, 151, 307, 313 
Scales 
as covering, 242 
cottony cushion, 89 
of life, 161 
of nature, 32 
of scent, 146 
Seallops, 315 
Scent, 67 
see also Odors, Scales 
Schmidt, 60 
Schuchert, 195, 340 
Science 
as arena, 169 
as thrashing-machine, 170 
nature of, 156, 168-177, 180, 
212, 230, 259, 336 
limits of, 161 
Scott, 254, 340 
Seals, 60, 246, 247 
Sedgwick, 186, 271, 278 
Seeds, 75 
other references, 69, 92, 119, 
125, 126 
Seeley, 247 
Selection 
natural, 136-160, 163, 318-329 
not creative, 134, 160 
other references, 88, 10, 125, 
127, 132, 156, 200, 274, 279, 
288, 290, 311, 312, 316, 329 
artificial, 231-235 
other references, 49, 103, 107, 
108, 128-130, 132, 140, 274, 
286, 313 


INDEX 


Semper, 328 


Senecio, 41 
Sequoias, 43 
Series, continuous of forms, 25, 
30, 31, 39, 47, 53, 54, 149, 151, 
154, 155, 185, 205, 207, 219, 
224" 227, 240, 242, 243, 249, 
250, 268, 269 
Sex 
chromosome of, 117 
differences, 48, 146 
groups, 152 
Shad, 59 
Sheep, 49, 101, 108, 141 
Shells, 178, 181, 198, 258, 315 
as measure of time, 183, 185-187 
Shirreff, 103, 314 
Siamese twins, 93 
among fishes, 94 
Silkworms, 67, 108, 116 
Silurian, 186, 198, 199 
Skulls, 193, 222 
Skunk, 52 
Sleeping-sickness, 48 
Blye, 298 
Smith, 183 
Snails, 206 
other references, 104, 206, 249 
Snakes, 44, 148, 155, 211, 243, 247 
Snow- plant, 89 
Somatic, see Body-cells, Environ- 
ment 
Sparrows, 80, 127 
Species 
artificial, 233 
as fixed, 32, 216-222 
Darwin’s conception, 274-275 
defined, 22, 32-39 
de Vries’s conception, 105, 301- 
303 


nature of, 218-223 
see also Extinct 
numbers of, 20-29 
other references, 30, 40, 53, 101, 
120, 133, 190, 204-206, 210, 
211, 218, 214, 227, 231, 233, 
261 
see also Selection, artificial 
Wallace’s conception, 276 
Spencer, 269 
Sperm, 330 
see also Germ-cell, Pollen 
Spiders, 28, 34, 156 
Splitters, 38, 39 


—— 
~~ ae 


INDEX 


Sponges, 28, 223-227, 238 
chart, 225 
picture, 68 
Sports, 101, 105, 181, 142, 234, 
302, 318 
Sports of nature, 181 
Spruces, 217-221 
Squids, 58, 238 
Squirrels, 42, 58, 207 
Stamens, 67 
see also Pollen 
Starch, 74 
Starfish, 90, 239 
Stevenson, 88 
Sting, 148, 154 
Strawberry, 106 
Structures, 236-251 
other references, 24, 64, 246 
see also Five-finger, Series con- 
tinuous, Bones, Feathers, 
Leaves, ete. 
Struggle for existence, 77-91 
picture, 86 
other references, 51, 57, 58, 66, 
69, 125, 126, 129, 145, 223, 
274 
see also Selection, Survival 
Sugar of leaves, 72 
Sugar factory, 96 
Sun, 191 
Sunflower, 102 
Survival of the fittest, 127, 136- 
160, 276 
see also Selection 
Sword-fish, 52 


Tahiti, 206 
Tails, 111 
Tasmanian wolf, 47, 52 
Tassel, 119 
Thayer, 61 
Theory, nature of, 173-175 
other references, 155, 168, 237, 
239, 250, 251 
see also Science, nature of 
Thinking, 54, 61, 63, 86-87, 113, 
137, 173 
see also Savage thinking 
Thomson, 340 
Thrush, 58 
Tigers, 61, 66 
Titanotheres, 193 
Toads, 46 
Toadstools, 23 
Tobacco, 234 


303 


Toes, 55, 135, 240, 252-254, 312 
sce also Five-finger 

Tracks, 178, 180, 241, 252 

Transformation, 319 
see also Mutation 

Transmutation, 174 

Tree of life, picture, 236 
references to, 43, 156, 225, 230, 

236, 251 

Trees, 44 

Tree-toads, 46 

Triceratops, 117 

Tsuga, 217 

Tuberculosis, 172 

Tumble-weeds, 69 

Turnip, 132 

Turtles, 201 

Tyrannosaur, 179 


Unit characters, 288, 296, 297, 330 
see also Genes, Chromosomes 


Variation 
defined, 100-101, 316-318 
explained, 92-109, 139-148, 163, 
290, 313-318 
general references to Variation, 
25, 49, 57, 114, 115, 121, 125- 
127,130,' 1387, 9.910,), 211-213) 
219, 234, 270, 287, 301, 309, 
310, 327, 328, 330 
in wild species, 106, 134, 145, 
235 
picture of, 102 
round trip in, 134, 136 
stimulated by environment, 131 
Variety 
defined, 35 
other references, 24-26, 37, 38, 
43, 101, 102, 142, 205, 207, 
211, 213, 227, 228, 231, 232 
pictures, 206, 207 
Veins 
of leaf, 74, 107 
of wing, 134 
Vertebrates, 33, 239, 242 
see also Mammals, Fishes, Prim- 
ates, etc. 
Vestigial structures, 247, 250 
Vicufia, 233 
Vinci, 181 
Virchow, 112 
Vitalism, 312 
Vivisection, 282 
Vries, de, 301-303 


304 INDEX 


Vries, de, con’t. Wheat, 26, 102, 130, 234, 314 
other references, 26, 105, 315, story of grains, 77 
318, 321, 340 White, 147 
see also Albino 
Waagen, 258 eee 
Reena meee Wilson, A., 80 
Wallace, 275-277 tne 


other references, 29, 38, 62, 64, Wilson, E. B., 100, 291, 318, 319, 


341 
107, 135, 325, 339, 340 
Walter, 112, 291, 296 — Windle, 333 


Wings, 241, 246-248 
Na Wolves, 39° 
Woah 334 see also Tasmanian 
{ Woodpeckers, 51, 54 
eo ceeataont Woodruff, 84, 160, 296, 316, 319, 
eb of life, 30 Bo aa 
Weeds, 41 ) 
Weevils, 34 Worms, 28, 83, 141, 156 


Weismann, 286-291 
other references, 21, 112, 120, Yale museum, 241, 244 
144, 146, 269, 320, 324, 327, Yucca, 60 
341 
Whales, 46, 246 Zebras, 61, 262 
2d hte Zoology, 341 


+ a 
me 
Wa ‘ 


% deg 


ie he : 


a oe i 





Date Due 





_— a 














| 


| 


il 


0146 419 


| 


iii 


| 


eological Ser 


Mh 


wii 


av 
oO 
(an) 
= 
< 
(oe) 
2 
im = 
oO 
~O 
fon) 
a 
Co 


Evolution 





